Ashwin Shetty and Shubha Tole at the TIFR, Mumbai

New Delhi, Nov. 18: Indian scientists have identified a gene that helps build the fine circuitry in the brain that could explain how people can distinguish between closely related shades of paints or tones on a musical instrument.

The researchers at the Tata Institute of Fundamental Research, Mumbai, have shown that a gene called Lhx2 plays a critical role in the development of the analogous brain circuitry in mice that allows them to use their whiskers to sense the world around them.

In experiments with mouse embryos, the TIFR researchers collaborating with institutions in the US and Taiwan have shown that mice that lose the Lhx2 gene while they are embryos fail to develop the sensory circuitry for efficient use of their whiskers.

“If we view their whiskers as fingers, then losing the Lhx2 gene is like wearing mittens that prevent us from using individual fingers,” Shubha Tole, a senior neurobiologist at the TIFR who led the study, told The Telegraph.

Ashwin Shetty, a PhD student in Tole’s laboratory, has shown that when the Lhx2 gene is knocked off in the region of the brain called the cortex on the 11th day of a typical 19-day gestation of mouse embryos, the fine circuitry underlying sensory information processing does not form. The findings appeared today in the US journal Proceedings of the National Academy of Sciences.

Although the nerves that carry signals from the whiskers do make connections with the brain’s sensory cortex, the circuitry that contributes to fine resolution and discrimination becomes “profoundly defective”, the researchers said.

Their study also provides fresh evidence for the idea gaining momentum that the Lhx2 gene functions like a master-switch, controlling several key functions that guide the development of the brain during embryonic life.

In earlier studies, the researchers had shown that Lhx2 coaxes embryonic brain cells to turn into cells that make up the cerebral cortex, the part of the brain involved in higher functions such as memory, thinking and language. Two years ago, research scholars in Tole’s laboratory showed that Lhx2 also controls the formation of brain cells that make up the hippocampus, a region of the brain involved in learning and memory.

“When the brain is being formed, all genes are not equal — some are more important than others, and Lhx2 appears to be one such gene,” Tole said. “It turns on at different periods of the embryonic phase with different functions.”

The new study provides insights into the mechanisms underlying the formation of the exquisitely detailed circuitry for processing certain sensory information, said Neeraj Jain, a neurobiologist at the National Brain Research Centre, Manesar (Haryana), who was not connected with the study. “We want to know how the brain is put together, and this work gives us an important piece that will go into that puzzle.”

The other team members at TIFR are Geeta Godbole, Hari Padmanabhan, Bhavana Muralidharan and Upasana Maheshwari. Their collaborators in the study are V. Rema and Rahul Chaudhary at the NBRC, Manesar, Edwin Monuki at the University of California, Irvine, and Hung-Chih Kuo and Pei-Shan at the Academia Sinica in Taiwan.