Mutations in the testis-specific NALP14 gene in men suffering from spermatogenic failure

Because of the common use of ICSI and the potential genetic aetiology of spermatogenic failure, concern has been raised about transmitting genetic disorders to ICSI offspring. However, to date, in only approximately 15% of all cases of spermatogenic failure, an underlying genetic cause can be identified. We have previously established an association between spermatogenic failure and chromosomal region 11p15. In this study, we set out to explore whether NALP14, a gene recently mapped to 11p15, has a function in spermatogenesis and whether mutations in NALP14 can cause spermatogenic failure.

We applied two different multiple tissue northern (MTN) blots to determine tissue specificity of NALP14 and performed immunohistochemistry on human testis with anti-NALP14 antiserum. To determine imprinting status of NALP14, we tested the expression pattern of two single-nucleotide polymorphisms (SNPs) in human testis. Finally, we performed a mutation screen of the NALP14 gene in 157 men with azoospermia or severe oligozoospermia by direct sequencing; 158 normospermic men served as controls.

NALP14 was, as are the three other genes in 11p15, exclusively expressed in testis. Within the testis, the NALP14 protein was mainly expressed in A dark spermatogonia, mid and late spermatocytes and spermatids. The mutation screen revealed five mutations that occurred only in the patient group. One of these unique mutations introduced an early stop codon in the NALP14 sequence, predicted to result in a severely truncated protein.

Our data suggest that NALP14 has a function in spermatogenesis and that mutations in this gene might cause spermatogenic failure.