Gene encoding a new RING-B-box-Coiled-coil protein is mutated in mulibrey nanism.

Mulibrey nanism (for muscle-liver-brain-eye nanism, MUL; MIM 253250) is an autosomal recessive disorder that involves several tissues of mesodermal origin, implying a defect in a highly pleiotropic gene. Characteristic features include severe growth failure of prenatal onset and constrictive pericardium with consequent hepatomegaly. In addition, muscle hypotonia, J-shaped sella turcica, yellowish dots in the ocular fundi, typical dysmorphic features and hypoplasia of various endocrine glands causing hormonal deficiency are common. About 4% of MUL patients develop Wilms' tumour. MUL is enriched in the Finnish population, but is rare elsewhere. We previously assigned MUL to chromosome 17q22-q23 and constructed a physical contig over the critical MUL region. The region has now been further refined by haplotype analysis and new positional candidate genes have been localized. We identified a gene with four independent MUL-associated mutations that all cause a frameshift and predict a truncated protein. MUL is ubiquitously expressed and encodes a new member of the RING-B-box-Coiled-coil (RBCC) family of zinc-finger proteins, whose members are involved in diverse cellular functions such as developmental patterning and oncogenesis.

Two XX males in one family and additional observations bearing on the etiology of XX males.

Two XX males who were second cousins are reported. A genetic mechanism producing maleness is suggested. The putative factor had been transmitted solely through males, which excludes the possibility of a heritable X-Y interchange. Recent reports on fluorescent Y chromatin in Sertoli cells of XX males prompted investigations into the fluorescence patterns of testicular cells. Sertoli cells from three XX males displayed brightly fluorescent spots, but it was concluded that they did not represent Y chromosomes. Evidence for this conclusion was obtained from the study of testicular fluorescence in XX, XXY and XY males. No visually detectalbe cytogenetic evidence for an increase in length or altered banding pattern of one of the X chromosomes was found in three XX males. We conclude that an autosomal gene is the most likely explanation of the male differentiation in the two XX males presented here.