Identification of the gene altered in Berardinelli-Seip congenital lipodystrophy on chromosome 11q13

Congenital generalized lipodystrophy, or Berardinelli-Seip syndrome (BSCL), is a rare autosomal recessive disease characterized by a near-absence of a dipose tissue from birth or early infancy and severe insulin resistance(1-4 ). Other clinical and biological features include acanthosis nigricans, hyp erandrogenism, muscular hypertrophy, hepatomegaly, altered glucose toleranc e or diabetes mellitus, and hypertriglyceridemia. A locus (BSCL1) has been mapped to 9q34 with evidence of heterogeneity(5). Here, we report a genome screen of nine BSCL families from two geographical clusters (in Lebanon and Norway). We identified a new disease locus, designated BSCL2, within the 2 .5-Mb interval flanked by markers D11S4076 and D11S480 on chromosome 11q13. Analysis of 20 additional families of various ethnic origins led to the id entification of 11 families in which the disease cosegregates with the 11q1 3 locus; the remaining families provide confirmation of linkage to 9q34. Se quence analysis of genes located in the 11q13 interval disclosed mutations in a gene homologous to the murine guanine nucleotide-binding protein (G pr otein), gamma3-linked gene(6) (Gng3lg) in all BSCL2-linked families. BSCL2 is most highly expressed in brain and testis and encodes a protein (which w e have called seipin) of unknown function. Most of the variants are null mu tations and probably result in a severe disruption of the protein. These fi ndings are of general importance for understanding the molecular mechanisms underlying regulation of body fat distribution and insulin resistance.