Innovations in Biotechnology and Medical Sciences

X chromosome revival in older Women increases Autoimmune Disease risk


From UPSC perspective, the following things are important :

Prelims level: Autoimmune Diseases, X Chromosome

Mains level: NA

Why in the News?

The X chromosome influences biological functions and disease susceptibilities, affecting genetic disorders, autoimmune diseases, and Alzheimer’s, with research offering potential new treatments and therapies.

Back2Basics: Chromosomes

  • Chromosomes are fundamental components of cells that play a vital role in storing and transmitting genetic information.
  • These structures contain genes, which carry instructions for the development, functioning, and inheritance of traits.
  • Chromosomes consist of tightly coiled DNA molecules wrapped around proteins called histones, forming chromatin.
  • Before cell division, chromosomes replicate into identical sister chromatids held together at the centromere.

Types of Chromosomes:

  1. Autosomes: Non-sex chromosomes (22 pairs in humans) determine most traits.
  2. Sex Chromosomes: Determine biological sex (XX for females, XY for males).

Functions of Chromosomes

  • Genetic Information Storage: Genes on chromosomes encode instructions for protein production and cellular processes.
  • Inheritance: Chromosomes transmit genetic information during sexual reproduction through meiosis, ensuring genetic diversity in offspring.
  • Gene Expression Regulation: Chromosomes control gene activation or silencing, crucial for development and cell functioning.

Genetic Landscape of the X chromosome:

  • The human X chromosome encodes around 800 genes, producing proteins.
  • Loss of function in these genes can lead to various genetic diseases.
  • Diseases influenced by the X chromosome fall into three categories:
  1. X-linked genetic diseases
  2. Diseases influenced by XCI (X chromosome inactivation) escape
  3. Diseases linked to X-chromosome aneuploidy

What is the X chromosome?

  • It is one of the two sex chromosomes in humans, the other being the Y chromosome.
  • Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
  • Significance:
    • Encodes around 800 genes that are crucial for various biological processes.
    • Plays a significant role in determining sex and influencing many physiological functions.
    • Loss of function or mutations in X chromosome genes can lead to several genetic disorders.

What are Autoimmune Diseases?

  • Diseases where the immune system mistakenly attacks the body’s own cells and tissues.
  • Normally, the immune system defends against infections by targeting harmful pathogens.
  • Common Autoimmune Diseases:
    • Systemic Lupus Erythematosus (SLE): Chronic inflammation affecting various body parts.
    • Rheumatoid Arthritis (RA): Inflammation of joints and surrounding tissues.
    • Sjogren’s Syndrome: Affects glands that produce moisture, leading to dry mouth and eyes.

How does the X chromosome cause Autoimmune Diseases?

  • X Chromosome Inactivation (XCI):
    • In females, one of the two X chromosomes is randomly inactivated during early embryonic development to balance gene expression between males and females.
    • This process is crucial to prevent overexpression of X-linked genes.
  • XCI Escape:
    • Not all genes on the inactive X chromosome are completely silenced.
    • Up to a fourth of these genes may escape inactivation and continue to be expressed.
  • Link to Autoimmune Diseases:
    • Skewed XCI: Uneven inactivation of X chromosomes may lead to an imbalance in gene expression, contributing to autoimmune disorders.
    • Incomplete XCI: Reactivation of genes that should be silenced can result in abnormal immune responses.

Studies, such as one published in Science Advances (May 3, 2023), have shown that reactivation of X-linked genes in immune cells can lead to lupus-like symptoms in mice.

Linkage between X chromosome and Alzheimer’s disease

  • Sex Bias in Alzheimer’s:
    • Women are almost twice as likely as men to develop Alzheimer’s disease.
  • Role of X-Linked Genes:
    • Researchers have identified a gene called ubiquitin-specific peptidase 11 (USP11) on the X chromosome.
    • USP11 Gene: Involved in protein modification processes and thought to influence the accumulation of tau proteins in the brain.
    • XCI Escape: USP11 may escape XCI in females, leading to higher expression levels and contributing to Alzheimer’s pathology.
    • A study from Case Western Reserve University (Cell, October 2022) highlighted this mechanism, suggesting it as a target for new treatments.


[2011] At present, scientists can determine the arrangement or relative positions of genes or DNA sequences on a chromosome. How does this knowledge benefit us?

  1. It is possible to know the pedigree of livestock.
  2. It is possible to understand the causes of all human diseases.
  3. It is possible to develop disease-resistant animal breeds.

Which of the statements given above is/are correct?

(a) 1 and 2 only

(b) 2 only

(c) 1 and 3 only

(d) 1, 2 and 3

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