Genetic Basis of Bart's Syndrome: A Glycine Substitution Mutation in the Type VII Collagen Gene

Angela M. Christiano, Bruce J. Bart, Ervin H. Epstein, Jouni Uitto
1996 Journal of Investigative Dermatology  
Oep<lrtments of *Dermatology and C utaneous Biol ogy, and §Bi ochcmi stry and Mol ecular Bi ology, J efferson Medi ca l Co llege, Philadelphia. Penn sylvan ia: ' i" f-I ennepin Co unty Medical Center, Mjnn eapolis. Minn esota; and :j:Dcpartl11 cnt of Dermatology, UniversilY of Cali fo rni a, San Francisco. San Francisco, Ca lifornia, U.S .A. Bart's syndrome was initially described as a genodermatosis characterized by congenital localized absence of the skin, together with blistering and nail
more » ... stering and nail abnormalities. Recent analysis of Bart's original kindred demonstrated ultrastructural abnormalities in the anchoring fibrils and linkage of the inheritance of the disease to the region of chromosome 3 near the type VII collagen gene (COL7Al). We have performed mutation analysis in this family by using electrophoretic heteroduplex analysis followed by direct nucleotide sequencing of DNA. These results B art's sy ndro m e, as origina ll y describe d ill a large family by Bart and his coll e agu es (Bart ci ai, 1966) , presents with con genital localize d absence of skin , us uall~ 'lffectin.g th.e lower ex tre. mities. The p atients late r di splay bhstenn g of the skin and mu co us m embranes, and nail absence and abnormalities . T h e synd rome is iI;1herited in an a utosom a l dominant fa shion, apparently with ftlll penetra n ce but with va ri abl e exp ressivi ty. Since the d escription of the origi nal famil y, similar patie n ts with associa ted fe a tures of diffe re n t sub types of epidermolysis bullosa (EB) hav e bee n re p o rted (B a rt, 1970; Smith and C ram , 1 9 78; Skoven and Drzew iecki, 1979; Wojnarowska e ( ai, 1983; Kanzler cl ai, 1992); h owe ve r, the molec ular basis of Bart' s syndro me has re mained uncl ea r. R ece ntl y, Bart and his coll eagu es revi sited the original family and th e ir descendants, and pe rto rm ed ex tensive clin ic"l , ultrastru ctural, and immuno fluorescen ce an alyses (Zelickson e( ai, 1995). The ultra stru ctural feature s de mon strated subl amina d e nsa bliste ring, w ith normal basa l keratin ocytes, to n o filam e nts. and hemidesm osome s. Ho wever, within the involved skin, the nnmbe r of anch orin g fibr ils wa s d ecreased and they were poorl y formed, su ggestin g that B ar t's syndrom e ma y b e a varia nt o f dOininant dystrophi c EB. Gen etic linkage analyses in the fa mily using an in tragenic polymo rphic m arker and a Rankin g mi crosa telli te (D3S1067) suggested t hat the Bart' s sy ndrome locus resides withi.n or near th e COL7 A1 ge n e (Zelickso n et ai, 1995), whic h has bee n ma pped to the short a rm of c hromosome 3 in th e p2 1 region (Pare nte et ai, 1991) . W e have rece ntl y cloned the e ntire human typ e VII co lla gen Manu 450 Blu cml e Life Sciences Bui ldin g, Philadelphia , PA 19107-5541. Abbre viation s: En. epidermolysis bull os"; CSGE. conformation-sensiti ve gel electroph ores is. disclosed a G-to-A transition within exon 73 01 COL7Al, which results in a glycine-to-arginine sub, stitution within the triple-helical domain of type VI.) collagen in affected individuals. In this family, thes~ findings demonstrate that Bart's syndrome is a clini, cal variant of dominant dystrophic epidermolysi~ bullosa. Key lVovds: domi1lant dystvopllic epide"1IIolys4 /J/Iliosalt}lpe VII collagen gelle l1Iutati011slml.cllOl'illg fi·bliis l cuta lleous basemellt membmlle z Olle. ] Illvest Del'll/atoll0 6~ 778-780, 1996 cDNA and elu c id ated th e intro n-exo n organizatio n of the COITt\ spondin g ge n e (COL7 A 1) (C hri stia no e ( ai, 1994a, 1994b). Tn dl~ study , we scree n ed COL7 A ' I fo r mutations ill t h e fam il y o ri ginalh, desc ribe d by B art ct al (1 966) . ' MATEIUALS AND MET HODS T he f;l111il y was o riginall y describ ed in 1966 by B;lrt el al (1966). and , subseq uent pubLication (Zclickson cI "/, 1995) delin ea ted the 1I1trastructul;;l\ features in this f<lJn il y. [1'1 this study, blood salllp les were obta in ed from 3~ indiviciu"l s. 22 of th em "fleeted and 17 unaffected. represe nting fOlll generations of th e fam il y. as depicted in Fig 1. Ge no mi c DNA WaS i solate~ (Sambrook " I ai, 1989). an d. initia ll y, two afFected individu als were su~ jeeted to mutati on screenin g by al11plifi cation of CO L7 A I exollS, foll owe<\ by heterodupl ex anal ysis usin g confonna tion-scnsitive gel c1ectrophores' (CSGE) (Ganguly el "I, 1993). as desc ribed elsew here (C hristiano el ni, 1995a). T he PCR prod uct demonstrating a hctcrod uplex was subj ected tI:\ auto mated nucleotide seq uencing (All I). The nucleotid e substitution d", reeted .in the affected individuals (a G-to-A transiti on at Ilucl eotid e positiQ~ 6007 within cxon 73) res ulted in loss of a restri ction enzyme site for Artl, Subsequently. the DNA fiOl11 the rel11ainjng 37 indi viduals waS tested fO t th e presence or abse nce of th is nucleotide substi tuti on by heteroduplc,\ analysi s and by Adl di ges tion. RESULTS AND DISCUSS ION DNAfi~om two affected indi viduals (nos. 1-4 and 11-13 in th~ ped ig ree ill (Fig 1) revea le d a h cterod u plex in a pol ym e rase chail\ reaction (PC R) pro du ct spanning exo n 73 (Fig 2A) . A s im ila~ h e te rod upl ex was su bsequently demon stra te d in all 22 affected, individuals tested (Fig 2A) . Tn contra st, Il o ne of t h e ] 7 ullaffecreq fu mil y m embers de m o nstrated the presen ce of h cterodupl ex . D irect se quen cin g of th e P C R pro du ct d em o ll strating the bet, e ro duplex rev ealed a G-to-A transition at nucl eo tid e position 600 in one of the aUeles whil e the other all ele contain ed the wi l d-t)'P~ G (Fig 2B) . T hi s nucleotid e change results in substitutio n of th~ cod o n for g lycine (CGG) by a codon fo r arginin e (AGG) in one Qt t he all e of the affected indi viduals. T hi s mu tation, des ignate4 0022-202X/96/S10.50 •
doi:10.1111/1523-1747.ep12346304 pmid:8618021 fatcat:ctm5h7w4nng7lb6fb7nwtn74mm