Mutations of t-complex testis expressed gene 5 transcripts in the testis of sterile t-haplotype mutant mouse.

Aim: To determine the possible roles of the t-complex testis expressed gene 5 (Tctex5) on sperm functions, the full-length sequence of mRNA was studied and compared in the testis between the normal wild-type and the sterile t-haplotype mutant mice.

Methods: We applied rapid amplification of cDNA ends, Northern blot and reverse transcription polymerase chain reaction to analyze the full length of Tctex5 mRNAs isolated from testes of the wild-type and the t-haplotype mice. Reverse transcription polymerase chain reaction was used to semi-quantitatively compare expression of Tctex5 transcripts in the 16 tissues and 9.5 day stage embryos in the wild-type mice. E-translation was applied to estimate the amino acid sequences.

Results: One long and one short transcript of Tctex5 mRNA were discovered in mouse testis of wild-type (Tctex5(long-+) and Tctex5(short-+)) and t-haplotype (Tctex5(long-t) and Tctex5(short-t)) mice, respectively. Being enhanced only in the testis, Tctex5(long-t) had 17 point mutations and one 15-bp-deletion in the exon 1 region, comparing with the Tctex5(long-+), whereas the Tctex5(short-t) was similar to the Tctex5(short-+). The short isoforms of Tctex5 mRNAs in the two models encoded exactly the same peptides, but the long isoforms did not. The estimated peptide encoded by Tctex5(long-t) had significant mutations on putative sites of phosphorylation and PP1 binding.

Conclusion: We established that mutations that occur in the Tctex5 long transcript of the t-haplotype mice are important for normal sperm function, whereas the short transcript of Tctex5 might have a conserved function among different tissues.