Deafness-Infertility Syndrome

A number sign (#) is used with this entry because it represents a contiguous gene deletion syndrome on chromosome 15q15.3. Two of the genes residing in this region are STRC (606440) and CATSPER2 (607249).

STRC alterations cause autosomal recessive nonsyndromic sensorineural deafness-16 (DFNB16; 603720).

Description

Deafness-infertility syndrome (DIS), characterized by early-onset deafness in both males and females and exclusive male infertility, is caused by homozygous deletion of the STRC and CATSPER2 genes on chromosome 15q15.5 (summary by Vona et al., 2015).

Clinical Features

Dgany et al. (2002) reported a nonconsanguineous French family in which a 56-year-old male and his 2 brothers suffered from type I congenital dyserythropoietic anemia (CDA1; 224120), infertility, and nonsyndromic deafness. Further examination of the 3 brothers by Avidan et al. (2003) revealed a moderate symmetric sensorineural hearing loss of 40 dB involving all frequencies. Semen analysis showed a normal volume and sperm concentration but abnormal motility and morphology, indicative of asthenoteratozoospermia.

Zhang et al. (2007) described 3 consanguineous unrelated Iranian families segregating autosomal recessive nonsyndromic deafness. In each family, affected individuals had prelingual auditory impairment with normal vestibular function and no syndromic features. Sperm motility was assessed in 3 males from 2 of the families, and all 3 had reductions in motility and viability consistent with asthenoteratozoospermia; in the third family, the only affected male was too young to assess.

Knijnenburg et al. (2009) described a 10-year-old boy, born of nonconsanguineous parents, who had progressive bilateral sensorineural hearing loss with moderate hearing impairment for all frequencies. He had mental retardation, short stature, normal head circumference, and dysmorphic features consisting of metopic ridge, low set ears, high nasal bridge and protruding columella, high-arched palate, small palpebral fissures, thick eyelashes, and synophrys. He also displayed brachydactyly and had intermittent swelling of hands and feet with no known cause.

Vona et al. (2015) reported 3 patients, including 2 boys and a girl, with onset of sensorineural deafness between birth and early childhood. All had homozygous deletions of the STRC and CATSPER2 genes. All were prepubertal at the time of study and were not evaluated for fertility. One boy had additional congenital abnormalities and comorbidities, which were likely independent of the deafness. The patients were ascertained from a larger cohort of 94 GJB2 (121011)/GJB6 (604418)-negative pediatric patients with sensorineural hearing loss who underwent genetic analysis.

Mapping

Zhang et al. (2007) performed a genomewide screen using STRP marker analysis in 2 consanguineous unrelated Iranian families with deafness and male infertility and identified a single region of homozygosity by descent in affected individuals on chromosome 15q15.1-q15.3.

Molecular Genetics

In 3 French brothers with type I CDA, asthenoteratozoospermia, and nonsyndromic deafness, Dgany et al. (2002) identified homozygosity for a point mutation within the codanin gene (607465.0003) as the cause of the type I CDA. Avidan et al. (2003) found that the 3 sibs were also homozygous for an approximately 70-kb deletion in chromosome 15q15, which removed the entire STRC gene and the last 2 exons (225 bp) of the CATSPER2 gene. Avidan et al. (2003) suggested that lack of functional stereocilin, which is mutated in DFNB16 (603720), and CATSPER2, a voltage-gated cation channel expressed exclusively in spermatozoa, might explain the observed deafness and male infertility phenotypes, respectively.

In 3 consanguineous Iranian families segregating nonsyndromic deafness and male infertility, Zhang et al. (2007) identified an approximately 100-kb deleted region on chromosome 15q15.3 involving KIAA0377 (610979), CKMT1B (123290), STRC, and CATSPER2. The families did not share identical deletions, and haplotype analysis indicated that they did not share a common ancestor. Zhang et al. (2007) noted that the hearing loss phenotype in these families was similar by audioprofiling to that of DFNB16, suggesting that deletion of STRC is causally related to their deafness.

In a 10-year-old boy, born of nonconsanguineous parents, who had progressive bilateral sensorineural hearing loss, mental retardation, and dysmorphic features, Knijnenburg et al. (2009) identified homozygosity for a 90-kb deletion on chromosome 15q15.3, containing 4 genes, including the STRC gene. The unaffected parents were hemizygous carriers. By screening healthy control individuals and reviewing publicly available copy number variation (CNV) data, Knijnenburg et al. (2009) estimated the frequency of hemizygous deletion carriers to be about 1.6%. The authors noted that this case illustrates the importance of not automatically eliminating registered CNVs from further analysis.