Genetic DiagnosticsAbout infertility
Genetic tests are now available to explore the cause of the infertility. Genetic factors include chromosomal abnormalities, single gene mutations and monogenic or multifactorial syndromes.
Depending on the existing problem, genetic testing is performed with one of the three following methodological approaches: chromosome analysis, molecular cytogenetics (fluorescence in situ hybridization, FISH) or molecular analysis of DNA.
Genetic testing should thus always begin with a classical chromosome analysis. If the karyotype is normal, molecular genetic analyses, especially in order to test for FMR1 gene mutations in premature ovarian failure and CYP21A2 mutations in polycystic ovaries and/or other symptoms of lateonset androgenital syndrome (21-hydroxylase deficiency),have to be considered.
FMR1 gene (Fragile X mental retardation 1) Mutations in the FMR1 gene located in the long arm of the X chromosome (Xq27.3) are differentiated into full mutations, premutations and intermediate alleles. Full mutations in the male cause the fragile X syndrome (FXS) with mental retardation and other associated symptoms.21-hydroxylase deficiency by a gene mutation can be a monogenic cause of infertility and often results in polycystic ovary syndrome in women.
In men with oligoospermia or azoospermia, molecular genetic testing confirms a high frequency of deletions in the long arm of the Y chromosome encompassing the azoospermia factor (AZF) region as well as, specific mutations in the CFTR gene. In cystic fibrosis, an autosomal-recessive disorder, patients are either homozygous or compound heterozygous for CFTR (Cystic fibrosis transmembrane conductance regulator) mutations. CFTR mutations can also result in unilateral aplasia of the vas deferens (AVD), which results in severe oligozoospermia.