New Delhi: A team of Indian researchers, steered by the All India Institute of Medical Sciences (AIIMS) here, has proposed a plausible mechanism that may explain how the Zika virus may cause microcephaly -- a rare birth defect where a baby is born with an abnormally small head -- and other brain defects. According to these researchers, the Zika virus interferes with retinoic acid (a metabolite of vitamin A) signalling by introducing its genome sequence repeats (called the Retinoic Acid Response Elements or simply RARE consensus repeats) into the developing brain cells of the fetus. This could be the mechanism by which Zika virus (ZIKV) infection may cause microcephaly in the fetuses of infected women, the researchers suggested in a study published in the journal Frontiers in Human Neuroscience. “The rationale of the mechanism of ZIKV-Microcephaly relationship is based on sequence homology between ZIKV genome and the response element of an early neural tube developmental marker (retinoic acid) in human DNA” said Himanshu Singh from AIIMS and his colleagues. The team of scientists was headed by Ashutosh Kumar and Muneeb Faiq from AIIMS. Other researchers at Dr. B.R. Ambedkar Centre for Biomedical Research, New Delhi, and National Brain Research Centre, Haryana, also contributed to the study. Zika is a severely pathogenic virus causing many brain malformations including microcephaly in neonates. Owing to the observation that this virus causes many neurological problems and severe birth defects, WHO declared this outbreak as the “Public Health Emergency of International Concern”, AIIMS said in a statement. Since this virus has the ability to get transferred from pregnant women to their fetuses, it has been observed to cause acute brain malformations and microcephaly. Many countries have advised their citizens to delay pregnancy till the mechanism by which this viruses causes microcephaly is deciphered. Understanding the mechanism of ZIKV mediated microcephaly is an immediate need of the hour that could help in preventing the spread of this epidemic and blocking the disease causing abilities of this virus. For the study, the researchers screened genomic sequences of already reported virulent ZIKV strains (including those linked to microcephaly) and other viruses available in the US National Institute of Health genetic sequence database (GenBank) for the RARE consensus.