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Genetic Mysteries of Microcephaly: The Role of SASS6 Gene


From UPSC perspective, the following things are important :

Prelims level: Microcephaly, SASS6 Gene, Ile62Thr Mutation

Why in the News?

A gene called SASS6 (Spindle Assembly Abnormal Protein 6) and its variants have been found to play a key role in a developmental process that causes “Microcephaly”.

What is Microcephaly?

  • Microcephaly is a condition where a baby’s head is much smaller than normal.
  • It is associated with a smaller brain, poor motor skills, poor speech, abnormal facial features, and intellectual disabilities.
  • Developmental Roots:
    • The condition is believed to start during the peak phase of brain development in the embryo. Cells that are supposed to become neurons fail to divide normally.
  • Diagnosis:
    • Microcephaly can be diagnosed before birth using foetal ultrasound and MRI.

Role of SASS6 gene 

  • Since 2014, the SASS6 gene and its variants have been linked to microcephaly.

A recent study in China:(On March 19, 2024)

  • The study of a consanguine couple revealed microcephaly and fetal growth issues. Confirming the SASS6 gene’s role in microcephaly, findings suggest embryo survival requires at least one functional gene copy.

The University of Cologne Study (February 2024):

  • Researchers removed all functional SASS6 genes from mouse embryo-derived cells.
  • Even without the genes, cells could make abnormal but passable centrioles (structures needed for cell division).
  • When these cells were prompted to become neurons, the centrioles disappeared, preventing the cells from becoming neurons.

Consanguinity and Genetic Risk of Microcephaly

  • Expert Insight:
    • Researchers explained that over 70% of congenital microcephaly cases come from consanguineous marriages.
    • Such marriages increase the risk of inheriting mutated genes from both parents.
  • Genetic Causes:
    • Mutations in 30 genes cause microcephaly.
    • 10 of these genes create proteins needed for centrioles, which are crucial for cell division.

Ile62Thr Mutation

  • 2004 Discovery: The SASS6 gene was discovered in the roundworm C. elegans, showing its conserved function across animals.
  • Gene Suppression in C. elegans:
    • Suppressing the SASS6 gene halted new centriole assembly, stopping development.
  • 2014 Study on a Pakistani Family: Researchers found four family members with microcephaly due to the Ile62Thr mutation in the SASS6 gene.
  • The Ile62Thr mutation was introduced into the C. elegans SASS6 gene.
  • The mutation alone did not significantly impair centriole function but became deadly when combined with another mutation.
  • In humans, this mutation causes microcephaly due to its impact on centriole function.



[2016]  In the context of the developments in Bioinformatics, the term ‘transcriptome’, sometimes seen in the news, refers to-

(a) a range of enzymes used in genome editing

(b) the full range of mRNA molecules expressed by an organism

(c) the description of the mechanism of gene expression

(d) a mechanism of genetic mutations taking place in cells

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