A translocation breakpoint cluster disrupts the newly defined 3′ end of the SNURF-SNRPN transcription unit on chromosome 15

Wirth, Jutta ; Back, Elke ; Hüttenhofer, Alexander ; Nothwang, Hans-Gerd ; Lich, Christina ; Groß, Stephanie ; Menzel, Corinna ; Schinzel, Albert ; Kioschis, Petra ; Tommerup, Niels ; Ropers, Hans-Hilger ; Horsthemke, Bernhard ; Buiting, Karin

In: Human Molecular Genetics, 2001, vol. 10, no. 3, p. 201-210

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    Summary
    Balanced translocations affecting the paternal copy of 15q11-q13 are a rare cause of Prader-Willi syndrome(PWS) or PWS-like features. Here we report on the cytogenetic and molecular characterization of a denovo balanced reciprocal translocation t(X;15)(q28;q12) in a female patient with atypical PWS. The translocation breakpoints in this patient and two previously reported patients map 70-80 kb distal to the SNURF-SNRPN gene and define a breakpoint cluster region. The breakpoints disrupt one of several hitherto unknown 3′ exons of this gene. Using RT-PCR we demonstrate that sequences distal to the breakpoint, including the recently identified C/D box small nucleolar RNA (snoRNA) gene cluster HBII-85 as well as IPW and PAR1, are not expressed in the patient. Our data suggest that lack of expression of these sequences contributes to the PWS phenotype