Fundamentals of Human Genetics

Transcription

1 Prt ntis Jny L. Wiggs. finition: h ntrl prinipls of humn gntis with rlvn to y iss. Ky Fturs n strutur n xprssion. Orgniztion n inhritn of th humn gnom. Muttions n linil phnotyps. ns thrpis. N N H NRL OM OF HUMN NS h rgultion of llulr growth n funtion in ll humn tissu is pnnt on th tivitis of spifi protin moluls. n turn, protin tivity is pnnt on th xprssion of th gns tht ontin th orrt N squn for protin synthsis. h N molul is oulstrn hlix. h strn is ompos of squn of four nuloti ss nin (), gunin (), ytosin (), n thymin () join to sugr n phospht. h orr of th ss in th N squn forms th gnti o tht irts th xprssion of gns. h oulstrn hlix is form s rsult of hyrogn oning twn th nuloti ss of opposit strns. h oning is spifi, suh tht lwys pirs with, n lwys pirs with. h spifiity of th hyrogn oning is th molulr sis of th urt opying of th N squn tht is rquir uring th prosss of N rplition (nssry for ll ivision) n trnsription of N into RN (nssry for gn xprssion n protin synthsis; Fig...). n xprssion gins with th rognition of prtiulr N squn ll th promotr squn s th strt sit for RN synthsis y th nzym RN polymrs. h RN polymrs rs th N squn n ssmls strn of RN tht is omplmntry to th N squn. RN is singlstrn nuli i ompos of th sm nuloti ss s N, xpt tht uril tks th pl of thymin. Humn gns (n gns foun in othr ukryoti orgnisms) ontin mny N squns tht r not trnslt into polypptis n protins. hs squns r ll intrvning squns or introns. ntrons o not hv ny known spifi funtion, n lthough thy r trnsri into RN y RN polymrs, thy r spli out of th initil RN prout (trm htronulr RN, or hnrn) to form th omplt mssngr RN (mrn). Untrnslt RN my hv spifi funtions. For xmpl, ntisns RN n miro RNs (mirn) ppr to rgult xprssion of gns. 2 h mrn is th tmplt for protin synthsis. Protins onsist of on or mor polyppti hins, whih r squns of spifi mino is. h squn of ss in th mrn irts th orr of mino is tht mk up th polyppti hin. niviul mino is r no y units of thr mrn ss, trm oons. rnsfr RN (trn) moluls in spifi mino is n rogniz th orrsponing thrs oon in th mrn. llulr orgnlls ll riosoms in th mrn in suh onfigurtion tht th RN squn is ssil to trn moluls n th mino is r lign to form th polyppti. h polyppti hin my pross y numr of othr hmil rtions to form th mtur protin (Fig...2). HUMN NOM Humn N is pkg s hromosoms lot in th nuli of lls. hromosoms r ompos of iniviul strns of N woun out protins ll histons. h omplx wining n oiling pross ulmints in th formtion of hromosom. h ntir olltion of humn hromosoms inlus 22 pir utosoms n two sx hromosoms. Womn hv two opis of th X hromosom, n mn hv on X n on Y hromosom (Fig...3). h st onsisting of on of h utosom s wll s oth sx hromosoms is ll th humn gnom. h hromosoml moluls of N from on humn gnom, if rrng in tnm n to n, ontin pproximtly 3.2 illion s pirs (p). h Humn nom Projt ws formlly gun in 990 with th fin gols to: intify ll th pproximtly 20,000 25,000 gns in humn N; trmin th squns of th 3 illion hmil s pirs tht mk up humn N; stor this informtion in pulily vill tss; improv tools for t nlysis; trnsfr rlt thnologis to th privt stor; n rss th on hlil turn = 3.4 nm SRUUR OF H N OUL HLX Sugr phospht kon n nitrognous ss sugr phospht kon ss Sprtion of iniviul strns llows N rplition 5 l 3 l 5 l originl hin nw hins forming 3 l originl hin nin thymin gunin ytosin Fig... Strutur of th N oul Hlix. h sugr phospht kon n nitrognous ss of h iniviul strn r rrng s shown. h two strns of N pir y hyrogn oning twn th pproprit ss to form th oulhlil strutur. Sprtion of iniviul strns of th N molul llows N rplition, tlyz y N polymrs. s th nw omplmntry strns of N r synthsiz, hyrogn ons r form twn th pproprit nitrognous ss.

2 ntis NRL OM OF MOLULR NS nulus ytoplsm hromosom N trnsription PKN OF N NO HROMOSOMS N oul hlix primry mrn mtur mrn prossing histon Nulosom nulosom plsm mmrn trnsltion protin nulr por nulr nvlop N 200 p of N xon intron intron spli out Solnoi Fig...2 h ntrl ogm of Molulr ntis. rnsription of N into RN ours in th nulus of th ll, tlyz y th nzym RN polymrs. Mtur mrn is trnsport to th ytoplsm, whr trnsltion of th o prous mino is link to form polyppti hin, n ultimtly mtur protin is prou. 2 thil, lgl, n soil issus tht my ris from th projt. On of th most importnt gols, th omplt squn of th humn gnom, ws omplt in rft form in tlogs of vrition in th humn gnom squn hv lso n omplt, with th mirostllit rpt mp in 994, 4 th rls of th HpMp from th ntrntionl HpMp onsortium in 2004, 5 n mor rntly tlog of vrints from th 000 gnoms projt. 6 SNP ( is ts listing singl nuloti polymorphisms (SNPs) tht r singllttr vritions in N s squn. SNPs r oun togthr to form hplotyps, whih r loks of SNPs tht r ommonly inhrit togthr. his ining ours through th phnomnon of linkg isquilirium. Within hplotyp lok, whih my xtn for 0,000 00,000 ss of N, th nlysis of only sust of ll SNPs my tg th ntir hplotyp. h ntrntionl HpMp projt hs prform n initil hrtriztion of th linkg isquilirium pttrns twn SNPs in multipl iffrnt popultions. h SNP hplotyp loks intifi n xmin for ssoition with humn iss, spilly ommon isorrs with omplx inhritn. Knowlg out th ffts of N vritions mong iniviuls n l to nw wys to ignos, trt, n prvnt humn iss. his pproh hs n us sussfully to intify th risk loi for grlt mulr gnrtion, 7 9 myopi, 0, primry opnngl gluom, 2 4 n Fuhs nothlil ystrophy. 5 Mitosis n Miosis n orr for lls to ivi, th ntir N squn must opi so tht h ughtr ll n riv omplt omplmnt of N. h growth phs of th ll yl trmints with th sprtion of th two sistr hromtis of h hromosom, n th ll ivis uring mitosis. for ll ivision, th omplt N squn is opi y th nzym N polymrs in pross ll N rplition. N polymrs is n nzym pl of th synthsis of nw strns of N using th xt squn of th originl N s tmplt. On th N is opi, th ol n nw opis of th hromosoms form thir rsptiv pirs, n th ll ivis suh tht on opy of h hromosom pir longs to h ll (Fig...4). Mitoti ll ivision prous ughtr ll tht is n xt rpli of th iviing ll. Mioti ll ivision is spil typ of ll ivision tht rsults in rution of th gnti mtril in th ughtr lls, whih om th rproutiv lls ggs (womn) n sprm (mn). Miosis gins with N rplition, follow y piring of th mtrnl n ptrnl hromosoms (homologous piring) n n xhng of gnti mtril hromtin strn hromtin loop ontins pproximtly 00, 000 p of N hromosom hromti Fig...3 h Pkging of N nto hromosoms. Strns of N r woun tightly roun protins ll histons. h N histon omplx oms furthr oil to form nulosom, whih in turn oils to form solnoi. Solnois thn form omplxs with itionl protins to om th hromtin tht ultimtly forms th hromosom. twn hromosoms y romintion (Fig...5). h homologous hromosom pirs lin up on th mirotuul spinl n ivi suh tht th mtrnl n ptrnl opis of th oul hromosoms r istriut to sprt ughtr lls. son ll ivision ours, n th oul hromosoms ivi, whih rsults in ughtr lls tht hv hlf th gnti mtril of somti (tissu) lls. S MNLN PRNPLS wo importnt ruls ntrl to humn gntis mrg from th work of rgor Mnl, nintnth ntury ustrin monk. h first is th prinipl of sgrgtion, whih stts tht gns xist in pirs n tht only on mmr of h pir is trnsmitt to th offspring of mting oupl. h prinipl of sgrgtion sris th hvior of hromosoms in miosis. Mnl s son rul is th lw of inpnnt ssortmnt, whih stts tht gns t iffrnt loi r trnsmitt inpnntly. his work lso monstrt th onpts of ominnt n rssiv trits. Mnl foun tht rtin trits wr ominnt n oul msk th prsn of rssiv gn. t th sm tim tht Mnl osrv tht most trits sgrgt inpnntly, oring to th lw of inpnnt ssortmnt, h unxptly foun tht som trits frquntly sgrgt togthr. h physil rrngmnt of gns in linr rry long hromosom is th

3 MO LL YL MO LL YL. ughtr lls ntriols nulus nulr nvlop ntrphs ipolr spinl fir plsm mmrn ytoplsm nulolus Prophs Prophs hismt primry ooyt primry sprmtoyt Mtphs nphs lophs lophs Promtphs sonry ooyt sonry sprmtoyt mirotuul spinl pol ntromr hromti Mtphs nphs Mtphs nphs qutoril pln (mtphs plt) lrg gg n polr ois sprmtis of qul siz Hploi gmts Fig...4 h Mitoti ll yl. uring mitosis, th N of iploi ll is rplit, whih rsults in th formtion of ttrploi ll tht ivis to form two intil iploi ughtr lls. xplntion for this surprising osrvtion. On vrg, romintion vnt ours on or twi twn two pir homologous hromosoms uring miosis (Fig...6). Most osrvl trits, y hn, r lot fr wy from on nothr on hromosom, suh tht romintion is likly to our twn thm, or thy r lot on ntirly iffrnt hromosoms. f two trits r on sprt hromosoms, or romintion vnt is likly to our twn thm on th sm hromosom, th rsultnt gmt form uring miosis hs 50% hn of inhriting iffrnt llls from h loi, n th two trits rspt th lw of inpnnt ssortmnt. f, howvr, th loi for ths two trits r los togthr on hromosom, with th rsult tht romintion vnt ours twn thm only rrly, th llls t h loi r pss to snnt gmts in phs. his mns tht th prtiulr llls prsnt t h loi in th offspring rflt th orinttion in th prnt, n th trits ppr to link. For xmpl, in Mnl s stuy of p plnts, urly lvs wr lwys foun with pink flowrs, vn though th gns for urly lvs n pink flowrs r lot t istint loi. hs trits r link, us th urly lf gn n th pinkflowr gn r lot los to h othr on hromosom, n romintion vnt only rrly ours twn thm. Romintion n linkg r th funmntl onpts hin gnti linkg nlysis. MUONS Muttions r hngs in th gn N squn tht rsult in iologilly signifint hng in th funtion of th no protin. f Fig...5 h Mioti ll yl. uring miosis, th N of iploi ll is rplit, whih rsults in th formtion of ttrploi ll tht ivis twi to form four hploi lls (gmts). s onsqun of th rossing ovr n romintion vnts tht our uring th piring of homologous hromosoms for th first ivision, th four hploi lls my ontin iffrnt sgmnts of th originl prntl hromosoms. For rvity, prophs n tlophs r not shown. N ROMNON Y ROSSN OVR romintion Fig...6 nti Romintion y rossing Ovr. wo opis of hromosom r opi y N rplition. uring miosis, piring of homologous hromosoms ours, whih nls rossovr twn hromosoms to tk pl. uring ll ivision, th romin hromosoms sprt into iniviul ughtr lls. prtiulr gn is mutt, th protin prout might not prou, or it might prou ut funtion poorly or vn pthologilly (ominnt ngtiv fft). Point muttions (th sustitution of singl s pir) r th most ommon muttions nountr in humn gntis. Missns muttions r point muttions tht us hng in th mino 3

4 ntis 4 RPROL RNSLOON norml 9 r (9) norml 22 r (22) Fig...7 Riprol rnslotion twn wo hromosoms. h Phillphi hromosom (rsponsil for hroni mylognous lukmi) is shown s n xmpl of riprol hromosoml trnslotion tht rsults in n norml gn prout rsponsil for linil isorr. n this s n xhng ours twn th long rm of hromosom 9 n th long rm of hromosom 22. i squn of th polyppti hin. h svrity of th missns muttion is pnnt on th hmil proprtis of th swith mino is n on th importn of prtiulr mino i in th funtion of th mtur protin. Point muttions lso my rs th lvl of polyppti proution us thy intrrupt th promotr squn, spli sit squns, or rt prmtur stop oon. n xprssion n fft y th insrtion or ltion of lrg loks of N squn. hs typs of muttions r lss ommon thn point muttions ut my rsult in mor svr hng in th tivity of th protin prout. spifi tgory of insrtion muttions is th xpnsion of trinuloti rpts foun in ptints fft y rtin nurognrtiv isorrs. n intrsting linil phnomnon, ntiiption, ws unrstoo on molulr lvl with th isovry of trinuloti rpts s th us of myotoni ystrophy. 6 Frquntly, offspring with myotoni ystrophy wr fft mor svrly n t n rlir g thn thir fft prnts n grnprnts. xmintion of th issusing trinuloti rpt in fft pigrs monstrt tht th svrity of th iss orrlt with th numr of rpts foun in th myotoni ystrophy gn in fft iniviuls. his phnomnon hs n osrv in numr of othr isss, inluing Huntington s iss. 7 hromosoml rrrngmnts my rsult in rks in spifi gns tht us n intrruption in th N squn. Usully, th rk in N squn rsults in trunt, unstl, ysfuntionl protin prout. Osionlly, th rokn gn fuss with nothr gn to us fusion polyppti prout, whih my hv novl tivity in th ll. Oftn, suh novl tivity rsults in n normlity in th funtion of th ll. n xmpl of suh fusion protin is th prout of th hromosom 9;22 trnslotion tht is ssoit with mny ss of lukmi (Fig...7). 8,9 st onsisting of on of h utosom s wll s n X or Y hromosom is ll hploi st of hromosoms. h norml omplmnt of two opis of h gn (or two opis of h hromosom) is ll iploiy. Rrly, s rsult of norml hromosom sprtion uring ll ivision, ll or orgnism my hv thr opis of h hromosom, whih is ll triploiy. triploi humn is not vil, ut som ptints hv n xtr hromosom or n xtr sgmnt of hromosom. n suh sitution, th normlity is ll trisomy for th hromosom involv. For xmpl, ptints with own synrom hv thr opis of hromosom 2, lso rfrr to s trisomy f on opy of pir of hromosoms is snt, th ft is ll hploiy. ltions of th X hromosom r frquntly th us of uhnn s musulr ystrophy. 2 Polymorphisms r hngs in N squn tht on t hv signifint iologil fft. hs N squn vrints my moify iss prosss, ut lon r not suffiint to us iss. Humn N squn is highly vril n inlus singl nuloti polymorphisms (SNPs), mirostllit rpt polymorphisms (20 50 p rpts of or squn), vril numr of tnm rpt polymorphisms (VNR, rpts of p of N), or lrgr insrtion ltions. 22 NS N PHNOYPS h rltionship twn gns n phnotyps is omplx. Mor thn on gnti ft n l to th sm linil phnotyp (gnti htrognity), n iffrnt phnotyps n rsult from th sm gnti ft (vril xprssivity). Rtinitis pigmntos is n xllnt xmpl of gnti htrognity, s it my inhrit s n Xlink, utosoml ominnt, utosoml rssiv, or igni trit, n mor thn 200 ustiv gns hv n intifi. 23 Othr oulr isorrs tht r gntilly htrognous inlu ongnitl trt, gluom, n grlt mulr gnrtion. iffrnt gns my ontriut to ommon phnotyp us thy fft iffrnt stps in ommon pthwy. Unrstning th rol of h gn in th iss pross n hlp fin th llulr mhnisms tht r rsponsil for th iss. For mny gns, singl muttion tht ltrs ritil sit in th protin rsults in n norml phnotyp. For som isss, th rsulting phnotyps r rmrkly similr rgrlss of th ntur of th muttion. For xmpl, wi vrity of muttions in R us rtinolstom. Othr isss, howvr, xhiit vril xprssivity, in whih n iniviul s muttion my rsponsil for svr iss, mil iss, or iss tht is not linilly ttl (inomplt pntrn). hr r mny xmpls of oulr iss monstrting vril xprssivity, inluing Kjr s utosoml ominnt opti trophy, 24 xnfl Rigr synrom, 25 n nirii. 26 iffrnt muttions in th sm gn n lso rsult in iffrnt phnotyps (llli htrognity). llli htrognity ounts for th iffrnt phnotyps of ominnt ornl stroml ystrophis us y muttions in th F/H3. 27 h phnotypi xprssion of muttion my pn on its lotion within gn. Suh vril xprssivity s on th lotion of th muttion is xmplifi y muttions in th rs gn, whih my us typil utosoml ominnt rtinitis pigmntos or mulr ystrophy pning on th position of th gnti ft. 28 PttRNS OF HUMN NHRN h most ommon pttrns of humn inhritn r utosoml ominnt, utosoml rssiv, Xlink rssiv, n mitohonril. Fig...8 shows xmpls of ths four inhritn pttrns. Othr inhritn pttrns lss ommonly nountr in humn iss inlu Xlink ominnt, igni inhritn (polygni), psuoominn, n imprinting. Fig...9 fins th nottion n symols us in pigr onstrution. utosoml ominnt issusing muttion tht is prsnt in only on of th two gn opis t n utosoml lous (htrozygous) is ominnt muttion. For xmpl, ptint with ominnt rtinitis pigmntos will hv ft in on opy of on rtinitis pigmntos gn inhrit from on prnt who, in most ss, is lso fft y rtinitis pigmntos. h othr opy of tht gn, th on inhrit from th unfft prnt, is norml (wil typ). fft iniviuls hv 50% hn of hving fft silings n 50% hn of pssing th norml gn to thir offspring; 50% of hilrn of n fft iniviul will fft. For ominnt iss, mls n fmls trnsmit th iss qully n r fft qully. ru ominnt llls prou th sm phnotyp in th htrozygous n homozygous stts. n humns, most iniviuls fft y iss us y ominnt lll r htrozygous, ut osionlly homozygous muttions hv n sri. n ss whr th homozygous iniviul is mor svrly fft thn th htrozygous iniviul, th iss is mor ppropritly not to inhrit s smiominnt trit. For xmpl, llls in th PX3 gn, using Wrnurg s synrom, r smiominnt, us homozygot with mor svr iss ompr with thir htrozygot rltivs hs n sri. 29 n som pigrs with n utosoml ominnt iss, som iniviuls who rry th ftiv gn o not hv th fft phnotyp. Howvr, ths iniviuls n still trnsmit th iss gn to offspring n hv fft hilrn. his phnomnon is ll ru pntrn. h gn rsponsil for rtinolstom (R) is only 90% pntrnt, whih mns tht 0% of th iniviuls who inhrit mutnt opy of th gn o not vlop th tumor. 30 utosoml Rssiv isss tht rquir oth opis of gn to norml for vlopmnt r inhrit s rssiv trits. Htrozygous rrirs of mutnt gns r

5 nrtion V V V PRNS OF NHRN Pigrs with n utosoml ominnt trit 2 3 Pigrs with n utosoml rssiv trit 2 3 Pigrs with n Xhromosoml inhritn 2 3 Fig...8 Pttrns of nhritn. For pigrs with n utosoml ominnt trit, pnl shows inhritn tht origints from prvious gnrtion, pnl 2 shows sgrgtion tht origints in th son gnrtion of this pigr, n pnl 3 shows n pprnt spori s, whih is tully nw muttion tht riss in th most rnt gnrtion. his muttion hs 50% hn of ing pss to offspring of th fft iniviul. For pigrs with n utosoml rssiv trit, pnl shows n isolt fft iniviul in th most rnt gnrtion (whos prnts r oligtory rrirs of th mutnt gn rsponsil for th onition), pnl 2 shows pir of fft silings whos fthr is lso fft (for th silings to fft, th mothr must n oligt rrir of th mutnt gn), n pnl 3 shows n isolt fft iniviul in th most rnt gnrtion who is prout of onsnguinous mrrig twn two oligt rrirs of th mutnt gn. For pigrs with n Xhromosoml trit, pnl shows n isolt fft iniviul whos iss is us y nw muttion in th gn rsponsil for this onition, pnl 2 shows n isolt iniviul who inhrit mutnt opy of th gn from th mothr (who is n oligt rrir), n pnl 3 shows sgrgtion of n Xlink trit through multignrtion pigr (50% of th ml offspring r fft, n thir mothrs r oligt rrirs of th iss). For pigrs with mitohonril trit, th pnl shows lrg, multignrtion pigr mn n womn r fft, ut only womn hv fft offspring.. Pigrs with mitohonril trit V fft ml fft fml unfft ml unfft ml, gn rrir (htrozygous) unfft fml unfft fml, gn rrir (htrozygous) usully linilly norml. h sm rssiv ft might fft oth gn opis, in whih s th ptint is si to homozygot. iffrnt rssiv fts might fft th two gn opis, in whih s th ptint is ompoun htrozygot. n fmily with rssiv iss, oth prnts r unfft rrirs, h hving on wiltyp gn (lll) n on mutnt gn (lll). h prnt hs 50% hn of trnsmitting th ftiv lll to hil. us hil must riv ftiv lll from oth prnts to fft, h hil hs 25% hn of ing fft (50% 50% = 25%), n 50% of th offspring will rrirs of th iss. f th prnts r rlt, thy my rrirs of th sm rr muttions, n thr is grtr hn tht rssiv iss n trnsmitt to offspring. Mls n fmls hv n qul hn of trnsmitting n inhriting th iss llls. XLink Rssiv Muttions of th X hromosom prou istintiv inhritn pttrns, us mls hv only on opy of th X hromosom n fmls hv two. Most Xlink gn fts r inhrit s Xlink rssiv trits. rrir fmls r typilly unfft us thy hv oth norml opy n ftiv opy of th issssoit gn. rrir mls r fft us thy only hv on ftiv X hromosom n thy o not hv norml gn opy to ompnst for th ftiv opy. ll of th ughtrs of n fft ml will rrirs of th iss gn us thy will inhrit th ftiv X hromosom. Non of th sons of n fft ml will fft or rrirs us thy will inhrit th Y hromosom. h hil of rrir fml hs 50% hn of inhriting th iss gn. f son inhrits th ftiv gn, h will fft. f ughtr inhrits th ftiv gn, sh will rrir. n importnt hrtristi of Xlink rssiv isorrs is tht mls nvr trnsmit th iss to sons irtly (mltoml trnsmission). Usully fml rrirs of n Xlink iss gn o not hv ny linil vin of th iss. Howvr, for som Xlink isss, mil linil fturs n foun in fml rrirs. For xmpl, in Xlink rtinoshisis, fft mls r svrly fft, whrs rrir fmls hv visully insignifint ut linilly ttl rtinl normlity. 3 Mil phnotypi xprssion of th iss gn n us y th pross of lyoniztion. n orr for mls (with on X hromosom) n fmls (with two X hromosoms) to hv qul lvls of xprssion of Xlink gns, fml lls xprss gns from only on of thir two X hromosoms. h ision s to whih X hromosom is xprss is m rly in mryognsis, n th lin of sning lls fithfully hrs to th rly hoi. s rsult, fmls r mosis, with som lls in h tissu xprssing th mtrnlly riv X hromosom n th rminr xprssing th ptrnlly riv X hromosom. Whn on of th X hromosoms rris n norml gn, th proportion of lls tht xprss th mutnt vrsus th norml gn in h tissu n vry. Fmls n lso fft y n Xlink rssiv iss if th fthr is fft n th mothr oinintlly is rrir of muttion in th iss gn. n this s, 50% of ughtrs woul fft, us 50% woul inhrit th X hromosom from th mothr rrying th iss gn, n ll th ughtrs woul inhrit th X hromosom from th fthr rrying th iss gn. us most Xlink isorrs r rr, th rrir frquny of iss gns in th gnrl popultion is 5

6 ntis 6 or or 2 3 norml fml norml ml singl r inits mting low, n th hn tht rrir fml woul mt with ml fft y th sm iss is quit low. Mitohonril nhritn Mitohonri r smll orgnlls lot in th ytoplsm of lls. hy funtion to gnrt P for th ll n r most unnt in lls tht hv high nrgy rquirmnts, suh s musl n nrv lls. Mitohonri hv thir own smll hromosom 6,569 p of N noing for 3 mitohonril protins, 2 riosoml RNs, n 22 trns. Muttions ourring in gns lot on th mitohonril hromosom us numr of isss, inluing Lr s hritry opti trophy 32 n Krns Syr synrom. 33 Muttions ourring on th mitohonril hromosom r inhrit only from th mothr us virtully ll humn mitohonri r riv from th mtrnl gg. Fthrs o not trnsmit mitohonri to thir offspring. lls vry in th numr of mitohonri thy ontin, n whn lls ivi, th mitohonri r ivi rnomly. s rsult, iffrnt lls n hv vrying numrs of mitohonri, n if frtion of th mitohonri ontin mutt gn, iffrnt lls will hv vrying proportion of hlthy vrsus mutnt mitohonri. h istriution of mutnt mitohonri is ll htroplsmy, n th proportion of mutnt mitohonri n vry from ll to ll n n lso hng with g. iffrns in th rltiv proportions of mutnt mitohonri n prtly xplin th osrv vril svrity of mitohonril isss n lso th vril g of onst of mitohonril isss. Psuoominn S PR NOON norml prnts n norml offspring, two girls n oy, in irth orr init y th numrs; n init gnrtions singl prnt s prsnt mns prtnr is norml or of no signifin to th nlysis oul r inits onsnguinous union (mting twn los rltivs) 2 6 frtrnl twins (not intil) intil twins numr of hilrn for h sx rkn squr or irl mns fft iniviul; rrow (whn prsnt) inits th fft iniviul is propositus, th ginning of th nlysis utosoml htrozygous rssiv Xlink rrir ort or stillorn Fig...9 si Pigr Nottion. ypil symols us in pigr onstrution r fin. his trm sris n pprnt ominnt inhritn pttrn u to rssiv fts in iss gn. his sitution riss whn prnt fft y rssiv iss (two norml opis of th iss gn) hs spous who is rrir of on norml opy of th iss gn. hilrn from this oupl will lwys inhrit ftiv gn opy from th fft prnt n will hv 50% hn of inhriting th ftiv gn opy from th unfft rrir prnt. On vrg, hlf of th hilrn will inhrit two ftiv gn opis n will fft. h pigr woul mimi ominnt pigr us of pprnt irt trnsmission of th iss from th fft prnt to fft hilrn n us pproximtly 50% of th hilrn will fft. Psuoominnt trnsmission is unommon, us fw popl r symptomti rrirs for ny prtiulr rssiv gn. or n n XLink ominnt nhritn his inhritn pttrn is similr to Xlink rssiv inhritn, xpt tht ll fmls who r rrirs of n norml gn on th X hromosom r fft rthr thn unfft. ll of th ml offspring r lso fft. nontinnti pigmnti is proly inhrit s n Xlink ominnt trit. fft fmls hv irrgulrly pigmnt trophi srs on th trunk n th xtrmitis n ongnitl vsulrity in th priphrl rtin with sonry rtinl novsulriztion. 34 his n othr Xlink ominnt isorrs our lmost lwys in fmls, n it is likly tht th X hromosom gn fts using ths isss r mryoni lthls whn prsnt in mls. igni nhritn n Polygni nhritn igni inhritn ours whn ptint hs htrozygous fts in two iffrnt gns, n th omintion of th two gn fts uss iss. niviuls who hv muttion in only on of th gns r norml. igni inhritn is iffrnt from rssiv inhritn, us th two muttions involv iffrnt iss gns. n som rtinitis pigmntos fmilis, muttion nlysis of th priphrin gn n th ROM gn show tht th fft iniviuls hror spifi muttions in oth gns. niviuls with muttion in only on opy of ithr gn wr unfft y th iss. 35 rillli inhritn hs n sri in som fmilis fft y rt il synrom (S). n ths pigrs, fft iniviuls rry thr muttions in on or two S gns (2 S gns hv n intifi), 36 n unfft iniviuls hv only two norml llls. n som fmilis, it hs n propos tht S my not singlgn rssiv iss ut omplx trit rquiring t lst thr mutnt llls to mnifst th phnotyp. his woul n xmpl of trillli inhritn. 37 f th xprssion of hritl trit or prisposition is influn y th omintion of llls t thr or mor loi, it is polygni. us of th omplx inhritn, onitions us y multipl llls o not monstrt simpl inhritn pttrn. hs omplx trits my lso influn y nvironmntl onitions. xmpls of phnotyps in ophthlmology tht xhiit omplx inhritn us of ontriutions of multipl gns n nvironmntl ftors r myopi, 38 grlt mulr gnrtion, 39 n ultonst opnngl gluom. 40 mprinting Som muttions giv ris to utosoml ominnt trits tht r trnsmitt y prnts of ithr sx, ut thy r xprss only whn inhrit from prnt of on prtiulr sx. n fmilis fft with ths isorrs, thy woul ppr to trnsmitt in n utosoml ominnt pttrn from on prnt (ithr th mothr or th fthr) n woul not trnsmitt from th othr prnt. Osionlly, th sm muttion givs ris to iffrnt isorr pning on th sx of th prnt trnsmitting th trit. hs prntl sx ffts r vin of phnomnon ll imprinting. lthough th molulr mhnisms rsponsil for imprinting r not ompltly unrstoo, it pprs to ssoit with N mthyltion pttrns tht n mrk rtin gns with thir prntl origin. 4 MOLULR MHNSMS OF SS utosoml ominnt isorrs inhrit s utosoml ominnt trits rsult from muttions tht our in only on opy of gn (i.., in htrozygous iniviuls). Usully, th prntl origin of th muttion os not mttr. Howvr, if th gn is sujt to imprinting, thn muttions in th mtrnl or ptrnl opy of th gn my giv ris to iffrnt phnotyps. Hploinsuffiiny Unr norml irumstns, h opy of gn prous protin prout. f muttion ours suh tht on opy of gn no longr prous protin prout, thn th mount of tht protin in th ll hs n ru y hlf. Muttions tht us rution in th mount of protin or l to intivtion of th protin r ll lossoffuntion muttions. For mny llulr prosss, this rution in protin quntity os not hv onsquns, i.., th htrozygous stt is norml, n ths muttions my inhrit s rssiv trits (s ltr stion). Howvr, for som llulr prosss thr is n solut rquirmnt for th full osg of protin prout, whih n only furnish if oth opis of

7 prtiulr gn r tiv. isss tht r us y inhritn of singl muttion ruing th protin lvl y hlf r inhrit s ominnt trits. inoffuntion ominnt Ngtiv fft utosoml ominnt isorrs n us y mutnt protins tht hv trimntl fft on th norml tissu. Muttions in on opy of gn my prou mutnt protin tht n umult s toxi prout or in som othr wy intrfr with th norml funtion of th ll. h mutnt protin my lso intrfr with th funtion of th norml protin xprss y th rmining norml opy of th gn, thus liminting ny norml protin tivity. t is possil to hv ginoffuntion muttions tht n lso ominnt ngtiv us th nw funtion of th protin lso intrfrs with th funtion of th rmining norml opy of th gn. utosoml n XLink Rssiv Rssiv isorrs rsult from muttions prsnt on oth th mtrnl n ptrnl opis of gn. Muttions rsponsil for rssiv iss typilly us loss of iologil tivity, ithr us thy rt ftiv protin prout tht hs littl or no iologil tivity or us thy intrfr with th norml xprssion of th gn (rgultory muttions). Most iniviuls htrozygous for rssiv isorrs, oth utosoml n Xlink, r linilly norml. N HRPY Muttions in th N squn of prtiulr gn n rsult in protin prout tht is not prou, works poorly, or hs quir novl funtion tht is trimntl to th ll. ns thrpis n involv livry of norml gn to iss tissu, rpling or ugmnting protin tivity with othr protins or smll moluls, rsing norml gn xprssion, or gnomiting thniqus to rpir th muttion. hrputi gns n livr to spifi tissus using moifi viruss s vtors 42 (Fig...0). sussful xmpl of this pproh is th rstortion of vision in nin mol of Lr s ongnitl murosis using rominnt nossoit virus rrying th norml gn (RP65). 43 Humn trils using similr pproh lso sussfully rstor vision in ptints with RP65 muttions. 44 isss us y muttions tht rt gn prout tht is strutiv to th ll (ominnt ngtiv or gin of funtion muttions) n to trt using iffrnt pproh. n ths ss, gns or oligonulotis in prtiulr ntisns moluls tht n ru xprssion of th mutt gn r introu into th ll. 45 n iting using RSPR/s9 (Fig...) is nothr potntilly usful pproh for gin of funtion or loss of funtion muttions. 46 Rnt vns hv prou highly potnt in vivo gn thrpy vtors for trgting rtin. 47 n ition, nw mthos r mrging to introu thrputi gns into mg tissu using nonvirl mhnisms s on nnothnology. 48 N HRPY USN RROVRUS VOR rtrovirus unpkgl hlpr provirus hrputi gn nginr into rtrovirus N Rominnt virus rplits in pkging ll thrputi humn gn rpl rtrovirl gns with thrputi humn gn pkging ll Rplit rominnt virus infts th trgt ll n insrts opis of th thrputi gn nulus RN rvrs trnsription N humn trgt ll thrputi gn prout virions Fig...0 n hrpy Using Rtrovirus Vtor. thrputi gn is nginr gntilly into th rtrovirus N n rpls most of th virl N squns. h rominnt virus tht rris th thrputi gn is llow to rplit in spil pkging ll tht lso ontins norml virus tht rris th gns rquir for virl rplition. h rplit rominnt virus is llow to inft th humn iss tissu, or trgt ll. h rominnt virus my inv th iss tissu ut nnot rplit or stroy th ll. h rominnt virus insrts opis of th norml thrputi gn into th host gnom n prous th norml protin prout.. 7

8 8 ntis N N USN RSPR/s gui sgrn sffol S rpir NHJ HR PM trgt muttion: 2929 nulus onor tmplt 3 3 U UUUU UUUU U UUUUUUUUU U U 3 5 U UUUUUU insrtions ltions pris rpir Fig... n iting Using RSPR/s9. h RSPR/sN ining rts oulstrn N rk (S), whih n rpir through nonhomologous n joining (NHJ) or homology irt rpir (HR) pthwys. Hr, th Strptoous pyogns s9 nuls, with N protospr jnt motif (PM) squn, hs n irt to trgt th rgion ontining th S 929 > (l30hr) muttion. h gui RN is omplmntry to th nonpm strn, n th N ut sit is thr nulotis from th PM squn. oul strn N rks typilly unrgo rpir y NHJ, whih rsults in ltions n insrtions of vril lngth. N niks r gnrlly rpir through HR, whr onor tmplt n us to inorport pris gnomi moifitions. (pt from Hung SS, Mughy, Swnn O, t l. nom nginring in ophthlmology: pplition of RSPR/s to th trtmnt of y iss. Prog Rtin y Rs 206;53: 20.) Hysi P, Young L, Mky, t l. gnomwi ssoition stuy for myopi n rfrtiv rror intifis susptiility lous t 5q25. Nt nt 200;42: Mguir M, Simonlli F, Pir, t l. Sfty n ffiy of gn trnsfr for Lr s ongnitl murosis. N ngl J M 2008;358: horlifsson, Wltrs, Hwitt W, t l. ommon vrints nr V n V2 r ssoit with primry opnngl gluom. Nt nt 200;42: Wiggs JL, Yspn L, Husr M, t l. ommon vrints t 9p2 n 8q22 r ssoit with inrs susptiility to opti nrv gnrtion in gluom. PLoS nt 202;8(4): ss th omplt rfrn list onlin t xprtonsult.om KY RFRNS 000 noms Projt onsortium. mp of humn gnom vrition from popultionsl squning. Ntur 200;467: ily JN, Loomis SJ, Kng JH, t l. nomwi ssoition nlysis intifis XNR2, XN2 n FOX s susptiility loi for primry opnngl gluom. Nt nt 206;48(2): rtz KH, oskulwong N, Ryu, t l. 22 protin n Fuhs s ornl ystrophy. N ngl J M 200;363(): Hins JL, Husr M, Shmit S, t l. omplmnt ftor H vrint inrss th risk of grlt mulr gnrtion. Sin 2005;308:49 2. Hn J, hompsonlowry J, Riss, t l. OP muttions n mitohonril N hplotyps in utosoml ominnt opti trophy. nt M 2006;8:27 25.

9 RFRNS. Wtson J, rik FH. Molulr strutur of nuli is: strutur for oxyrios nuli i. Ntur 953;7: stllr M. Nonoing RNs in humn iss. Nt Rv nt 20;2(2): Wolfsrg, Mntyr J, Shulr. ui to th rft humn gnom. Ntur 200;409: Murry J, utow KH, Wr JL, t l. omprhnsiv humn linkg mp with ntimorgn nsity. ooprtiv Humn Linkg ntr (HL). Sin 994;265: h ntrntionl HpMp onsortium. h ntrntionl HpMp Projt. Ntur 2003;426: noms Projt onsortium. mp of humn gnom vrition from popultionsl squning. Ntur 200;28: Hins JL, Husr M, Shmit S, t l. omplmnt ftor H vrint inrss th risk of grlt mulr gnrtion. Sin 2005;308: Son JM, Yu Y, Millr, t l. Rr vrints in F, 3 n 9 r ssoit with high risk of vn grlt mulr gnrtion. Nt nt 203;45(): Fritsh L, gl W, ily JN, t l. lrg gnomwi ssoition stuy of grlt mulr gnrtion highlights ontriutions of rr n ommon vrints. Nt nt 206;48(2): Hysi P, Young L, Mky, t l. gnomwi ssoition stuy for myopi n rfrtiv rror intifis susptiility lous t 5q25. Nt nt 200;42: Vrhovn VJ, Hysi P, Wojihowski R, t l. nomwi mtnlyss of multinstry ohorts intify multipl nw susptiility loi for rfrtiv rror n myopi. Nt nt 203;45(3): horlifsson, Wltrs, Hwitt W, t l. ommon vrints nr V n V2 r ssoit with primry opnngl gluom. Nt nt 200;42: Wiggs JL, Yspn L, Husr M, t l. ommon vrints t 9p2 n 8q22 r ssoit with inrs susptiility to opti nrv gnrtion in gluom. PLoS nt 202;8(4): ily JN, Loomis SJ, Kng JH, t l. nomwi ssoition nlysis intifis XNR2, XN2 n FOX s susptiility loi for primry opnngl gluom. Nt nt 206;48(2): rtz KH, oskulwong N, Ryu, t l. 22 protin n Fuhs s ornl ystrophy. N ngl J M 200;363: Linl K, Shlling M. xpn rpt squns n iss. Smin Nurol 999;9: L JM, Rmos M, L JH, t l. rpt xpnsion in Huntington iss trmins g t onst in fully ominnt fshion. Nurology 202;78: Kto, Kurhshi H, mnul S. hromosoml trnslotions n plinromi rih rpts. urr Opin nt v 202;22(3): Vlrnu M, Müllriow, um H, t l. Molulr mrkrs gui ignosis n trtmnt in Phillphi hromosomngtiv myloprolifrtiv isorrs (Rviw). Onol Rp 200;23: Rourtoux PL, Krlhu. risomy 2: from hromosoms to mntl rtrtion. hv nt 2006;36: Soltnzh P, Friz MJ, unn, t l. linil n gnti hrtriztion of mnifsting rrirs of M muttions. Nuromusul isor 200;20: Littl PF. Strutur n funtion of th humn gnom. nom Rs 2005;5: igr SP, Sullivn LS, own SJ. ns n muttions using rtinitis pigmntos. lin nt 203;84(2): Hn J, hompsonlowry J, Riss, t l. OP muttions n mitohonril N hplotyps in utosoml ominnt opti trophy. nt M 2006;8: Hjlt, Smin V. urrnt molulr unrstning of xnfl Rigr synrom. xprt Rv Mol M 2005;7: Vinnt M, lli R, Olivir, t l. Vril phnotyp rlt to novl PX 6 muttion (VS4+5>) in fmily prsnting ongnitl nystgmus n fovl hypoplsi. m J Ophthlmol 2004;38: Shmt, Silv MM, Zii, t l. Molulr ss of ornl nothlil ystrophis. xp y Rs 202;95: Stuk MW, only SM, Nsh M. RS funtionl omins n ysfuntion in iss. v xp M iol 206;854: Wollnik, ukl, Uygunr O, t l. Homozygous n htrozygous inhritn of PX3 muttions uss iffrnt typs of Wrnurg synrom. m J M nt 2003;22: Hrour JW. Molulr sis of lowpntrn rtinolstom. rh Ophthlmol 200;9: Sikkink SK, isws S, Prry NR, t l. Xlink rtinoshisis: n upt. J M nt 2007;44: Nwmn NJ. Hritry opti nuropthis: from th mitohonri to th opti nrv. m J Ophthlmol 2005;40: Shmil J, Jkson S, Shfr J, t l. Mitohonril ytopthis. J Nurol 2003;250: Shils L, gl R Jr, Shh RM, t l. Multifol hypopigmnt rtinl pigmnt pithlil lsions in inontinnti pigmnti. Rtin 2006;26: Kjiwr K, rson L, ryj P. igni rtinitis pigmntos u to muttions t th unlink priphrin/rs n ROM loi. Sin 994;264: Shffil V. h lin ling th os: th molulr pthophysiology of humn osity synrom. rns m lin limtol sso 200;2: ihrs R, Lwis R, Ktsnis N, t l. rillli inhritn: rig twn Mnlin n multiftoril trits. nn M 2004;36: Hornk M, Young L. Myopi gntis: rviw of urrnt rsrh n mrging trns. urr Opin Ophthlmol 2009;20: nglis MM, Silvir, rr, t l. ntis of grlt mulr gnrtion: urrnt onpts, futur irtions. Smin Ophthlmol 20;26: Wiggs JL, Psqul LR. ntis of gluom. Hum Mol nt 207;26(R):R Lwis, Rik W. How imprinting ntrs work. ytognt nom Rs 2006;3: nntt J, hung, Mguir. n livry to th rtin: from mous to mn. Mthos nzymol 202;507: ln M, guirr, Ry J, t l. n thrpy rstors vision in nin mol of hilhoo linnss. Nt nt 200;28: Mguir M, Simonlli F, Pir, t l. Sfty n ffiy of gn trnsfr for Lr s ongnitl murosis. N ngl J M 2008;358: Plltir R, ron SO, Puymirt J. RN s gn thrpy for ominntly inhrit isss. urr n hr 2006;6: Hung SS, Mughy, Swnn O, t l. nom nginring in ophthlmology: pplition of RSPR/s to th trtmnt of y iss. Prog Rtin y Rs 206;53: Zinn, Pourt S, Khyhuk V, t l. n silio ronstrution of th virl volutionry ling yils potnt gn thrpy vtor. ll Rp 205;2(6): Vsir JK, Lhstwr V. Polymri nnoprtils for gn livry. xprt Opin rug liv 2006;3: