Restricted expression of the human DAZ protein in premeiotic germ cells

• Published in: Human reproduction (Oxford) Vol. 23; no. 6; pp. 1280 - 1289
• Main Authors: Huang, William J., Lin, Yi-Wen, Hsiao, Kuang-Nan, Eilber, Karyn S., Salido, Eduardo C., Yen, Pauline H.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.06.2008; Oxford Publishing Limited (England)
• Subjects: Adult; Biological and medical sciences; Blotting, Western; DAZ; DAZL; Deleted in Azoospermia 1 Protein; Gene Expression; Gynecology. Andrology. Obstetrics; Humans; Male; male infertility; Medical sciences; Meiosis; Original; Protein Isoforms - biosynthesis; Reverse Transcriptase Polymerase Chain Reaction; RNA-Binding Proteins - biosynthesis; spermatogenesis; Spermatogenesis - genetics; Spermatogonia - metabolism; DAZL; spermatogenesis; DAZ; male infertility; Human; Vertebrata; Mammalia; Spermatogenesis; Male sterility; Germinal cell; Male genital diseases; Protein
• ISSN: 0268-1161; 1460-2350
• DOI: 10.1093/humrep/den099

BACKGROUND The role of the Y chromosome-encoded Deleted in Azoospermia (DAZ) gene family in spermatogenesis remains unclear. The ability of men without the DAZ gene to produce sperm, as well as the lack of selective pressure on DAZ exon sequences during evolution, casts doubts on its functional significance. Most men have four DAZ genes encoding protein isoforms that differ significantly in size. However, published western blots showed only a single “DAZ” band, raising the possibility that not all four DAZ genes are expressed. METHODS RT–PCR, western blotting and immunostaining were used to study the expression of the four DAZ genes and the autosomal DAZL gene in human testes and in tissue culture cells. RESULTS RNA transcripts of all four DAZ genes were found in the testis, but at much lower levels than that of the DAZL transcripts. Expression in cultured somatic cells showed that DAZ transcripts encoding multiple DAZ repeats were translated inefficiently. No DAZ proteins could be unambiguously identified on western blots when the testicular samples from three patients without the DAZ genes were used as negative controls. Nonetheless, low levels of DAZ were detected in the cytoplasm of spermatogonia by immunostaining. CONCLUSIONS The expression of DAZ proteins in adult human testes is restricted to the spermatogonia and suggests a premeiotic role.