This report describes a fly model of azoospermia, Sertoli cell-only syndrome. In humans, there are both Y-linked and X-linked forms of this syndrome. Hypomorphic mutations in the Drosophila gene bel, which encodes a DEAD-box RNA helicase, have been found to result in the specific loss of germline cells in the testis, whereas somatic cells are maintained; this phenotype recapitulates that observed for Sertoli cell-only syndrome. Classical loss-of-function alleles, RNAi-targeting constructs, and alleles caused by insertional mutagenesis have been generated for the Dmel\bel gene.
One of the two human orthologs of Dmel\bel, DEAD-box helicase 3, Y-linked (DDX3Y), is within the region of the Y chromosome implicated in Sertoli cell-only syndrome. The second orthologous human gene, DDX3X, is located on the X chromosome. Neither human gene has been introduced into flies.
Homozygous amorphic alleles of Dmel\bel are lethal; hypomorphic mutations result sterility or semi-sterility in both sexes. Unlike the human DDX3 genes, the Dmel\bel gene is located on an autosomal chromosome; there are no closely related paralogs in Drosophila. Genetic and physical interactions of Dmel\bel have been described; see below and in the bel gene report.
[updated Jun. 2017 by FlyBase; FBrf0222196]