A Novel Frameshift Microdeletion of the TEX12 Gene Caused Infertility in Two Brothers with Nonobstructive Azoospermia

Male infertility is a growing health problem, which affects approximately 7% of the global male population. Nonobstructive azoospermia (NOA) is one of the most severe forms of male infertility caused by genetic defects, including chromosome structural abnormalities, Y chromosome microdeletions, or single-gene alterations. However, the etiology of up to 40% of NOA cases is unidentified. By whole-exome sequencing, we detected a homozygous 5-bp-deletion variant in exon 4 of the TEX12 gene (c.196-200del, p.L66fs, NM_031275.4) in two brothers with NOA of a nonconsanguineous Vietnamese family. This deletion variant of 5 nucleotides (ATTAG) results in a premature stop codon in exon 4 and truncation of the C-terminal. Segregation analysis by Sanger sequencing confirmed that the deletion variant was inherited in an autosomal recessive pattern. The 1st and 3rd infertile sons were homozygous for the deletion, whereas the 2nd fertile son and both parents were heterozygous. The new deletion mutation identified in TEX12 gene caused loss of function of TEX12 gene. The loss of TEX12 function has already caused infertility in male mice. Therefore, we concluded that the loss of TEX12 function may cause infertility in men. To our knowledge, this is the first case reported so far indicating disruption of human TEX12, which leads to infertility in men.

Chapter 7 Human Epididymal and Testicular Sperm Cryopreservation

Since the advent of intracytoplasmic sperm injection (ICSI) in the early 1990s, surgical techniques to recover samples from the epididymis and testis directly have been used to benefit patients suffering from obstructive and nonobstructive azoospermia. Various studies have demonstrated comparable fertilization, ongoing pregnancy, and implantation rates when fresh and frozen-thawed epididymal sperms were used for ICSI [1]. Injection of fresh and frozen testicular sperms into mature oocytes resulted in similar fertilization rates in cases of obstructive azoospermia. However, in cases of nonobstructive azoospermia, the outcome depends upon the degree of impairment of spermatogenesis, criteria for sperm freezing, and patient selection [2].