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Current Affairs

Mutation in smell gene associated with asthma

Date: 24 December 2019 Tags: Miscellaneous

Issue

A multi-institutional study by Indian researchers has shown that a variant of an olfactory gene (OR2AG2) is a novel candidate for asthma. This is the first time in India a four-generation large family with high asthma prevalence has been studied for the said purpose.

 

Background

The gene was validated in a north Indian cohort of 141 children with asthma and 130 controls. About 80% of children with asthma carried a copy of the gene variant.

 

Details

  • Twenty individuals representing the four generations were selected for studying. Of the 20 persons studied, 14 had asthma and the rest served as a control group. 

  • While whole genome genotyping helps in detecting variations across the genome, the exome sequencing allows variations in the protein-coding region of any gene to be identified.

  • Researchers turned to computer modelling to narrow down the possible variants that might be responsible for asthma and finally confirmed the genetic variant through conventional sequencing.

  • Mutation in the sensory pathway such as olfaction is a plausible mechanism for increased asthma risk because of inability to mount an appropriate counter response. The inability to mount a counter response could lead to lung damage.

  • The inability to smell was assumed be a potential mechanism for lung damage and further study was conducted in this regard.

  • The researchers evaluated the ability of the 20 participants to smell a sweet odour and the concentration at which they could identify the odour. All 14 family members with asthma had one copy of the gene variant.

  • Healthy individuals and those with asthma were able to identify and differentiate different smells, but those with asthma could detect smells only at higher concentrations.

  • To validate the hypothesis, the researchers directly measured the gene expression in lung samples of those with asthma and normal subjects. In people with asthma, there was significant reduction in the expression of the gene.

  • There is either a genetic defect in the OR2AG2 gene at birth leading to suppressed expression or there is acquired suppression of gene expression later in life due to inflammation or environmental factors.