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Computer genetic metrics of fly brain reveal sex differences

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Neurons and glial cells of the ventral nerve cord (spinal cord analog) of Drosophila larvae. Credit: B. McCabe (EPFL)

Thanks to genetic tools that allow computers to accurately count neurons from microscopic images, EPFL researchers have unprecedented accuracy in counting the number of neurons and other types of cells in the brain of fruit fly larvae. Estimated, we found that women have substantially more neurons than men.

Determining the number of cells in the brain is the key to studying the structure and function of the brain.But count the neurons from Microscope image It takes time and the human eye is easily exhausted.To overcome this problem, researchers usually slice Brain tissue Then count the number of cells in one section to estimate the total number of neurons in the brain. However, these methods are error prone because they assume that the number of neurons or other cells is the same throughout the brain. Now, EPFL scientists have developed a new approach to identify cells in the intact brain of Drosophila larvae, an important neuroscience model organism, with superhuman accuracy and speed.

The results show that there are fewer neurons and more glial cells (a type of cell that supports and protects neurons) than previously thought. The team also found that there was an unexpected difference between the brains of male and female larvae, and that females had substantially more neurons than males.

“Currently, scientists are trying to get robots and computers to solve problems traditionally solved by humans,” said a study, director of the Institute for Neurogenetics and Diseases and a professor at the EPFL School of Life Sciences. Said Brian McCabe, senior author of. “We try to meet the computer along the way by making it easier to solve the problem.” For example, when a neuroscientist sees it. Nerve cell, Label the entire surface of the cell. However, neurons can have very complex structures. Like other cells, neurons have a rounded perikaryon in which the nucleus and other cell structures are located. But neurons have something that other cells don’t have. It is a complex process that extends from the cell body and transports electrical and chemical signals inside and outside the cell. “It’s very difficult for a computer to measure,” McCabe says.

Weijao, a post-doctor scientist in the McCabe lab who worked on Drosophila larvae, and her colleagues used genetic tools to represent fluorescent tags that only illuminate the nucleus of a neuron. They then imaged the larval brain using advanced microscopy techniques that allowed researchers to create 3D images of the sample without damaging it. Finally, the team asked the computer to inspect and analyze the microscopic images. “In these images, neurons are just points, and machine vision doesn’t have to look for complex 3D shapes, it just counts the points,” says McCabe.

Computer genetic metrics for fly brain reveal gender differences

Schematic diagram of a pipeline of molecular genetics, microscopy, and computational techniques used to count cells throughout the brain of Drosophila larvae. Credit: B. McCabe (EPFL)

Using this approach, the team has about 10,300 neurons in the female larval brain, 15-30% less than previously estimated, and about 3,800 glial cells, three times more than previously predicted. I found that.

The male larval brain has about 9,400 neurons, nearly 10% less than the female brain. However, the researchers found that they had about 4% more glial cells than their female counterparts. “and Larval stageDrosophila have no external genitals, so it was amazing to find such a big difference, “says McCabe.

Further analysis conducted by a mathematician led by Kathryn Hess, director of the Institute of Topology and Neuroscience and professor of EPFL life sciences, confirmed gender differences in the brain. When researchers analyzed the data using a method from the field of mathematics called topology to study the shape of the data, they were able to predict the sex of the animal from the topology of the brain with 99% accuracy. .. “The overall structure in which the male brain emerges looks different from that of the female brain,” Hess says.The survey results have been published at eLife..

Currently, there is no explanation for these gender differences, but McCabe speculates that behavioral differences may contribute to changes in the number of neurons. Glia cells Between the male and female brains. However, he adds, the findings emphasize that researchers need to look at both sexes when studying behavior and brain wiring.

Researchers have accurately determined the number of brain cells in Drosophila larvae, so how would you like to investigate? Neuron What are the functions of being connected to each other and having them? brain..To do so, McCabe plans to use a similar set of technologies to link. Genetic tools From Imaging to Computer-Aided Data Analysis — An approach that researchers call “robogenetics” or computer genetics. Robogenetics could turbocharge computer-based data analysis and allow theorists to explore biological data, McCabe says. He adds that such an interdisciplinary approach is one of the goals of the newly opened EPFL Imaging Center, a hub of advanced imaging and analysis.


Researchers detect diffusion barriers in flies’ brains


For more information:
Wei Jiao et al, Cellular quantification of the intact Drosophila central nervous system reveals sexual dimorphism, eLife (2022). DOI: 10.7554 / eLife.74968

Journal information:
eLife


Quote: Computer genetic metrics for flies’ brains were obtained from https: //phys.org/news/2022-07-genetic-metrics-brain-reveal-sex.html on July 19, 2022. (July 19, 2022) will be revealed

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