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Repeated MDA5 Gene Loss in Birds: An Evolutionary Perspective
Veronika Krchlíková1, Tomáš Hron1, Martin Těšický2
1Institute of Molecular Genetics of the Czech Academy of Sciences, 14220 Prague, Czech Republic.
Viruses
|November 27, 2021
Summary
Melanoma differentiation-associated protein 5 (MDA5) gene loss occurred independently in storks and rallids. This loss did not trigger compensatory evolution in the RIG-I gene, suggesting potential impacts on avian immune responses.
Area of Science:
- Immunology
- Genomics
- Evolutionary Biology
Background:
- Cytosolic receptors RIG-I and MDA5 detect viral RNA, initiating antiviral responses via interferon-stimulated genes (ISGs).
- Gene loss or pseudogenization of these receptors is rare, with MDA5 pseudogenization previously noted only once in mammals.
Purpose of the Study:
- To investigate MDA5 gene disruption in avian lineages.
- To determine if MDA5 loss impacts RIG-I evolution or function.
Main Methods:
- Screening of over 100 avian genome sequences.
- Analysis of selection pressures using RELAX and dN/dS methods.
Main Results:
- Independent MDA5 pseudogenization identified in storks and rallids.
- RELAX analysis confirmed no negative selection on the MDA5 pseudogene.
- dN/dS analyses showed no compensatory evolution in the RIG-I gene.
Conclusions:
- MDA5 pseudogenization has occurred independently in two distinct avian groups.
- The loss of MDA5 does not appear to have led to compensatory changes in RIG-I.
- MDA5 pseudogenization may significantly affect immune responsiveness in storks and rallids.
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