Structure and function of the deleted in azoospermia gene

A number of genes have been associated with variation in human spermatogenesis related to fertility. One of these, the Deleted in Azoospermia (DAZ) gene, exists as copies on two chromosomes, 3 and Y. The autosomal copy, DAZ-like (DAZL), has one RNA recognition motif (RRM) and is homologous to the DAZL gene found throughout the vertebrate lineage. There are four copies of DAZ on the Y chromosome with a pair at each of two sites. One pair contains a single RRM and the other has three RRMs. Human DAZ is homologous to genes in old world primates and ape Y chromosomes. Both DAZ and DAZL bind messenger RNAs at U-rich sequences near the poly-A tail in a manner that facilitates translation. Both are expressed in spermatogonia during the transition from mitotic cellular expansion through meiotic chromosomal reduction and during spermiogenesis. This study examined genomic variation in DAZ and DAZL, including deletion of DAZ from individuals with various levels of sperm cell production and mutations of DAZL in male partners of infertile couples. Deletions in DAZ are not as common in azoospermic men from central Texas as compared to other reports. Single nucleotide polymorphisms (SNPs) were identified in anonymous infertility patients, but were not located in the exons of the RRM. Proteins produced from transcripts encoded by genes from human DAZL, DAZL with SNPs within and outside the RRM, and a DAZ with single RRM were identified. Binding activity of DAZL to mRNA was confirmed using a microarray method, and mRNA from human testes was screened to identify at least 1,313 mRNA potential targets for DAZL. These targets were involved in ribosome construction, pyruvate metabolism, cell cycle control, and proteasome function. Variations in binding of protein to a high and a low bound target mRNA were demonstrated between protein constructs of DAZL, DAZL with mutations, and DAZ. Binding of DAZL to mRNA was also confirmed using electrophoretic mobility shift assays. With materials and procedures developed during this study, comparisons of genetic variants of DAZ and DAZL can be performed to identify mechanisms responsible for structural and functional differences in control of spermatogenesis.