Biology blurs line between sexes, behaviors

Date:
August 10, 2020
Source:
University of Rochester Medical Center
Summary:
Biological sex is typically understood in binary terms: male
and female.

However, there are many examples of animals that are able to modify
sex- typical biological and behavioral features and even change
sex. A new study identifies a genetic switch in brain cells that
can toggle between sex-specific states when necessary, findings
that question the idea of sex as a fixed property.



FULL STORY ========================================================================== Biological sex is typically understood in binary terms: male and female.

However, there are many examples of animals that are able to modify
sex-typical biological and behavioral features and even change sex. A new study, which appears in the journal Current Biology, identifies a genetic switch in brain cells that can toggle between sex-specific states when necessary, findings that question the idea of sex as a fixed property.


==========================================================================
The research -- led by Douglas Portman, Ph.D., an associate professor
in the University of Rochester Department of Biomedical Genetics and
the Del Monte Institute for Neuroscience -was conducted in C. elegans, a microscopic roundworm that has been used in labs for decades to understand
the nervous system. Many of the discoveries made using C. elegans apply throughout the animal kingdom and this research has led to a broader understanding of human biology. C. elegans is the only animal whose
nervous system has been completely mapped, providing a wiring diagram
-- or connectome -- that is helping researchers understand how brain
circuits integrate information, make decisions, and control behavior.

There are two sexes of C. elegans, males and hermaphrodites. Though the hermaphrodites are able to self-fertilize, they are also mating partners
for males, and are considered to be modified females. A single gene,
TRA-1, determines the sex of these roundworms. If a developing worm
has two X chromosomes, this gene is activated and the worm will develop
into a female. If there is only one X chromosome, TRA-1 is inactivated,
causing the worm to become a male.

The new study shows that the TRA-1 gene doesn't go completely silent in
males, as had been previously thought. Instead, it can go into action when circumstances compel males to act more like females. Typically, C. elegans males prefer searching for mates over eating, in part because they can't
smell food as well as females do. But if a male goes too long without
eating, it will dial up its ability to detect food and acts more like a
female. The new research shows that TRA-1 is necessary for this switch,
and without it hungry males can't enhance their sense of smell and stay
locked in the default, food- insensitive mate-searching mode. TRA-1 does
the same job in juvenile males - - it activates efficient food detection
in males that are too young to search for mates.

"These findings indicate that, at the molecular level, sex isn't binary or static, but rather dynamic and flexible," said Portman. "The new results suggest that aspects of the male nervous system might transiently take
on a female 'state,' allowing male behavior to be flexible according to internal and external conditions." A separate study appearing Current
Biology by a team of collaborating researchers at Columbia University
further describes the complex molecular mechanism by which TRA-1 is
controlled by sex chromosomes and other cues.

Additional co-authors of the study include Hannah Lawson, Leigh Wexler,
and Hayley Wnuk with the University of Rochester. The research was
supported with funding from the National Institute of General Medical
Sciences.


========================================================================== Story Source: Materials provided by
University_of_Rochester_Medical_Center. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Hannah N. Lawson, Leigh R. Wexler, Hayley K. Wnuk, Douglas
S. Portman.

Dynamic, Non-binary Specification of Sexual State in the
C. elegans Nervous System. Current Biology, 2020; DOI:
10.1016/j.cub.2020.07.007 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200810140949.htm

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