Intended purpose
The SALSA MLPA Probemix P461 STRC-CATSPER2-OTOA is an in vitro diagnostic (IVD)¹ or research use only (RUO) semi-quantitative assay² for the detection of deletions or duplications in the STRC, CATSPER2 and OTOA genes, as well as gene conversions between STRC and its pseudogene STRCP1, in genomic DNA isolated from human peripheral whole blood specimens. P461 STRC-CATSPER2-OTOA is intended to confirm a potential cause for and clinical diagnosis of Deafness-infertility syndrome (STRC and CATSPER2), Autosomal recessive deafness 16 (STRC) and Autosomal recessive deafness 22 (OTOA) and for molecular genetic testing of at-risk family members.

Copy number variations (CNVs) detected with P461 STRC-CATSPER2-OTOA should be confirmed with a different technique. In particular, CNVs detected by only a single probe always require confirmation by another method. Numerous defects in the STRC and OTOA genes are point mutations, none of which will be detected by MLPA. It is therefore recommended to use this assay in combination with sequence analysis.

Assay results are intended to be used in conjunction with other clinical and diagnostic findings, consistent with professional standards of practice, including confirmation by alternative methods, parental evaluation, clinical genetic evaluation, and counselling, as appropriate. The results of this test should be interpreted by a clinical molecular geneticist or equivalent.

This device is not intended to be used for standalone diagnostic purposes, pre-implantation or prenatal testing, or for the detection of, or screening for, acquired or somatic genetic aberrations.

¹ Please note that this probemix is for In Vitro Diagnostic (IVD) use in the countries specified at the end of this product description. In all other countries, the product is for Research Use Only (RUO).
² To be used in combination with a SALSA MLPA Reagent Kit and Coffalyser.Net analysis software.

Clinical background
Deafness-infertility syndrome (DIS; OMIM # 611102) is characterized by early-onset deafness in males and females and infertility exclusively in males. The hearing loss in DIS patients is non-progressive and the vestibular function is normal. Furthermore, the degree of hearing loss is moderate to severe. DIS is inherited in an autosomal recessive manner, as a contiguous gene deletion syndrome resulting from a homozygous deletion of the CATSPER2-STRC genes.

The STRC gene has also been associated to autosomal recessive deafness 16 (DFNB16; OMIM # 603720), a nonsyndromic hearing loss, with prelingual onset. The auditory phenotype in DFNB16 is similar to the auditory phenotype in DIS, where the hearing loss is moderate to severe. DFNB16 is caused by homozygous or compound heterozygous mutations, small indels, multi-exon or complete STRC deletions, as well as gene conversions between the STRC gene and its pseudogene (STRCP1) which are located less than 100 kb from each other (Moteki et al. 2016, Vona et al. 2015).

CNVs are a common cause of nonsyndromic hearing loss, STRC CNVs are the most common followed by CNVs in OTOA and GJB6 (Shearer et al. 2014). Homozygous or compound heterozygous missense, splice site mutations or complete OTOA deletions cause autosomal recessive deafness 22 (DFNB22; OMIM # 607039). DFNB22 has a prelingual onset, and the degree of hearing loss has been reported as moderate to severe and severe to profound.

More information is available at:
DIS: https://www.omim.org/entry/611102; https://www.ncbi.nlm.nih.gov/books/NBK598310/;
Hereditary hearing loss and deafness: https://www.ncbi.nlm.nih.gov/books/NBK1434/;
DFNB16: https://www.omim.org/entry/603720;
DFNB22: https://www.omim.org/entry/607039.

Probemix content
The SALSA MLPA Probemix P461-B1 STRC-CATSPER2-OTOA contains 45 MLPA probes with amplification products between 124 and 490 nt. This includes seven probes for the STRC gene, five probes for the CATSPER2 gene and ten probes for the OTOA gene. Multiple flanking probes are included for the aforementioned genes in the 15q15.3 and 16q12.2 regions, indicating the extent of possible CNVs. Furthermore, four STRCP1 probes are present, for which the results should be interpreted together with the STRC probes for the respective exon as rearrangements or gene conversions can occur (see Table 1 Probe pairs, in the Product Description). In addition, 11 reference probes are included that detect autosomal chromosomal locations. Complete probe sequences and the identity of the genes detected by the reference probes are available online (www.mrcholland.com).

This probemix contains nine quality control fragments generating amplification products between 64 and 105 nt: four DNA Quantity fragments (Q-fragments), two DNA Denaturation fragments (D-fragments), one Benchmark fragment, and one chromosome X and one chromosome Y-specific fragment. More information on how to interpret observations on these control fragments can be found in the MLPA General Protocol and online at www.mrcholland.com.