Explained | Scientists finally decipher enigmatic Y chromosome, feat to help study male infertility

In a significant achievement set to redefine the realm of human biology, scientists have successfully sequenced the Y chromosome for the first time. The breakthrough translates into the unearthing of valuable information about human genetic material that could revolutionise the study of male infertility and various health disorders.

Initial attempts to decipher the fundamental elements of our genetic code occurred two decades ago, yet significant gaps persisted across the 23 pairs of human chromosomes. These gaps were substantially filled last year by an international collective of 100 researchers known as the Telomere-to-Telomere (T2T) Consortium.

Why is it a major scientific breakthrough?

Add WION as a Preferred Source

This is because the Y chromosome is the most intricate of all chromosomes.

More than half of the sequences within the Y chromosome remained a mystery despite the purported success of the Human Genome Project and the T2T consortium. But now a group of scientists has completed the missing parts, unveiling a comprehensive Y chromosome sequence.

The findings were published in the journal Nature.

Monika Cechova, co-lead author of the study, remarked in an official statement, "Just a few years ago, half of the human Y chromosome was missing (from the reference)." She further added, "This is really a huge shift in what’s possible."

Ordinarily, humans possess a pair of sex chromosomes within each cell, with males inheriting an X and a Y chromosome, while females possess two X chromosomes.

What does it mean?

The newfound precision within the updated Y reference sequence will facilitate the exploration of conditions and disorders tied to this chromosome, including infertility due to inadequate sperm production.

Recent research also underscores the Y chromosome's broader importance in matters of health and longevity.

Also watch |Researchers fully sequence the Y chromosome for the first time

Professor Kenneth Walsh from the University of Virginia School of Medicine told CNN that certain genes on the Y chromosome are pivotal for preventing cancer and cardiovascular diseases.

Termed the "dark matter" of the genome, the Y chromosome has remained enigmatic.

However, this new analysis offers insights into its regulatory functions, as well as the potential encoding of mRNA and proteins.

“Genes have been identified on the Y chromosome that has been shown to be required for the prevention of cancer and cardiovascular disease,” Walsh reportedly told CNN via email.

“The Y chromosome has represented the ‘dark matter’ of the genome,” he added. “This new analysis will allow us to better understand the regions of the Y chromosome that have regulatory functions and may encode mRNA and proteins.”

As people age, especially in cells with rapid turnover such as blood cells, the Y chromosome starts to dwindle. The reasons and health implications behind this phenomenon have been unclear, though recent research suggests links to severe bladder cancer and heightened heart disease risk.

A comprehensive genetic reference for the Y chromosome may shed light on these connections.

According to Walsh, this research represents just the tip of the iceberg in comprehending the Y chromosome's role in age-related diseases, potentially contributing to the understanding of men's shorter lifespans compared to women.

How complex is the Y chromosome?

The Y chromosome contains over 30 million repetitive letters among its total of 62.5 million, often termed satellite or junk DNA.

It also contains palindromes—sequences of letters that read the same backwards and forward.

Unravelling the mystery posed a challenge due to its repetitive nature.

This repetition complicated the process of assembling data from genetic sequencing, likened to reading a book cut into strips where repetition obscures the original order.

Yet, advanced "long-read" sequencing technology and computational methods enabled researchers to achieve a complete reading of the Y chromosome.

This accomplishment added over 30 million repetitive base pairs to the human reference genome.

This year, researchers compiled a "pangenome," including DNA from individuals worldwide, enhancing inclusivity in the human genome. Alongside this, a collaborative team assembled Y chromosomes from diverse populations, capturing genetic variation.

Charles Lee, a senior author of the collaborative research paper, highlighted the vital role of proper Y chromosome gene function for men's overall health. He emphasized that their study empowers future sequencing endeavours to delve into health and disease aspects through comprehensive Y chromosome inclusion.

Y chromosome infertility

Y chromosome infertility is a common genetic condition that affects male fertility. It occurs in approximately 1 in 2,000 to 1 in 3,000 males of all ethnic groups.

It accounts for about 13 per cent of azoospermia (absence of motile sperm in semen) and 5 per cent of severe oligospermia (low sperm count) cases. Y-chromosome microdeletions, a specific type of genetic mutation, are known to cause this condition.

The Y chromosome plays a crucial role in male fertility, as it contains various genes, such as SRY (Sex-determining Region Y), and SOX9 (SRY-Box Transcription Factor 9), responsible for the development of the testes and the production of sperm. However, even a small portion of the Y chromosome missing can have significant consequences, such as reduced sperm production or a complete absence of sperm in the semen, leading to infertility.

The complete sequencing of the Y chromosome means that cause of this exact infertility can now be precisely ascertained and treated.

WATCH WION LIVE HERE

You can now write for wionews.com and be a part of the community. Share your stories and opinions with us here.