Azoospermia factor (AZF) in Yq11: towards a molecular understanding of its function for human male fertility and spermatogenesis

The Y chromosomal azoospermia factor (AZF) is essential for human spermatogenesis. It has been mapped by molecular deletion analyses to three subintervals in Yq11, AZFa, AZFb, and AZFc, containing a number of genes of which at least some control, post-transcriptionally, the RNA metabolism of other spermatogenesis genes, functionally expressed at different phases of the spermatogenic cycle. Intrachromosomal recombination events between homologous large repetitive sequence block in Yq11 are now recognized as the major cause of the AZFa, AZFb and AZFc microdeletions, and an overlap of the AZFb and AZFc regions was revealed by sequence analysis of the complete Yq11 region. The increasing knowledge of the expression patterns of AZF genes in human germ cells suggests that the DBY gene is the major AZFa gene, the RBMY gene the major AZFb gene, although a functional expression of the other AZFa/b genes in the male germ line is also most likely. Genetic redundancy might exist in AZFc because a number of gene copies in the large P1 palindrome structure in distal AZFc were found to be deleted also in fertile men.