12 Aug Study Shows Known Genes Associated with Male Infertility Doubled
Discovering the human genome sequence helps researchers understand how the instructions coded in DNA lead to a functioning human being.
In a recent study, thirty-three genes associated with male infertility have been identified through a genomics-first approach to identifying the condition. Researchers from the King Faisal Specialist Hospital and Research Centre in Saudi Arabia used exome sequencing, a technique for sequencing all the protein-coding regions of genes in a genome, to verify a genetic basis for infertility in male patients.
Patients with severe oligospermia and nonobstructive azoospermia were examined using exome sequencing (ES) parallel with the conventional practice of chromosomal analysis.
What is a Gene?
A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some, not all genes — act as instructions to make molecules called proteins. In humans, genes differ in size from a few hundred DNA bases to over 2 million.
Every individual has two copies of each gene — one derived from each parent. Most genes are identical in all individuals, but a small number of genes (less than 1 percent of the total) are distinctive. These minor DNA variations impact the unique physical features of each person.
What is Exome Sequencing?
The human genome consists of 3 billion nucleotides of DNA. Only a minute percentage of those nucleotides are translated into proteins, the functional players in the body. The exome consists of all the genome’s exons, which are the coding portions of genes.
Exome sequencing grants a look into the genome that large-scale studies cannot produce. Exome sequencing can reveal rare mutations that GWAS will not uncover. Exome sequencing is used for rare mutations.
Understanding the Numbers: Male Infertility
Of the 285 patients included in the study, 237 presented with nonobstructive azoospermia, a failure to make sperm — resulting in no sperm in the ejaculate. The remaining 48 patients displayed severe oligospermia, characterized by a sperm count lower than one million sperm. An equal number of fertile men were recruited to the study.
Of the 285 patients in the study:
- 10.5% had evidence of chromosomal aberrations
- 24.2% had a potential monogenic form of male infertility
The latter ranged from variants in genes previously reported to cause male infertility with or without other phenotypes in humans.
“The thirty-three candidate genes we identified in this study represent the largest number of male infertility genes discovered by a single study,” stated lead researcher, Dr. Fowzan Alkuraya. “There are only around 40 genes linked to nonobstructive azoospermia in humans. Thus, our study nearly doubles the genes linked to this phenotype.”
The study was conducted to understand the molecular biology behind male infertility, alongside more excellent application of genomic medicine to improve male fertility treatment and diagnosis.