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Baby Turtle Turns Into a Male, Adding Fresh Dimensions to Temperature-Dependent Sex Determination Theory

Inching closer to cracking the 50-year-old puzzle of how temperature turns baby turtles male or female, researchers have uncovered a molecular link that connects temperature with sexual development. In turtles and other reptiles, whether an egg hatches male or female depends on the temperature of its nest.

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The phenomenon was first discovered in reptiles more than 50 years ago, but until now the molecular details were a mystery.
turtle, representational image, pixabay
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Inching closer to cracking the 50-year-old puzzle of how temperature turns baby turtles male or female, researchers have uncovered a molecular link that connects temperature with sexual development.

In turtles and other reptiles, whether an egg hatches male or female depends on the temperature of its nest.

The phenomenon was first discovered in reptiles more than 50 years ago, but until now the molecular details were a mystery.

In a study published in the journal Science, the researchers said they have finally identified a critical part of the biological “thermometer” that turns a developing turtle male or female.

The explanation lies not in the DNA sequence itself — the A’s, T’s, C’s and G’s — but in a molecule that affects how genes are expressed without altering the underlying genetic code, the researchers said.

"This is the first functional evidence of a molecular link that connects temperature with sexual development," Capel said.
turtle eggs, pixabay

“Temperature-dependent sex determination has been a puzzle for a really long time,” said Blanche Capel, Professor at Duke University in North Carolina, US.

“This is the first functional evidence of a molecular link that connects temperature with sexual development,” Capel said.

Unlike humans and most other mammals, the sex of many turtles, lizards, and alligators is not determined by the chromosomes they inherit, but by ambient temperatures during a sensitive stage of development.

For a common pond and pet turtle called the red-eared slider, for example, eggs incubated at 32 degrees Celsius produce all female hatchlings, while those kept at 26 degrees Celsius hatch as males.

In the study, the researchers showed that cooler egg incubation temperatures turn up a key gene called Kdm6b in the turtle’s immature sex organs, or gonads.

This, in turn, acts as a biological “on” switch, activating other genes that allow testes to develop.

Unlike humans and most other mammals, the sex of many turtles, lizards and alligators is not determined by the chromosomes they inherit, but by ambient temperatures during a sensitive stage of development.
turtles, pixabay

To home in on the critical Kdm6b gene, the researchers took a group of freshly laid turtle eggs, incubated them at either 26 or 32 degrees Celsius, and looked for differences in the way genes were turned on in the turtles’ gonads early in development — before their fate as ovaries or testes has been decided.

Further experiments showed that the protein encoded by the Kdm6b gene, in turn, interacts with a region of the genome called Dmrt1, which acts as a master switch to turn on testis development.

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“The next step is to find the temperature-sensing trigger,” said study co-author Ceri Weber, a Ph.D. candidate in the Capel lab at Duke.

“We’re trying to narrow down the possibilities,” Weber added. (IANS)

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New Gene Responsible For Rare Genetic Hair Loss Discovered

However, the discovery of the gene already contributes to an improved diagnosis of the rare disease

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New gene for rare genetic hair loss discovered. IANS

Researchers have deciphered a new gene responsible for a rare form of genetic hair loss condition.

Hypotrichosis simplex occurs without other abnormalities. In infancy, fine hair tends to sprout sparsely. With increasing age, hair loss progresses. Ultimately, only a few hair is left on the head and body.

A team of researchers from the University Hospital of Bonn found that changes in the lanosterol synthase (LSS) gene lead to impairment of an important enzyme that has a crucial function in cholesterol metabolism.

However, the cholesterol blood values of those affected are not changed, the finsings showed.

“There is an alternative metabolic pathway for cholesterol, which plays an important role in the hair follicle and is not related to blood cholesterol levels,” said Regina C. Betz from the University’s Institute of Human Genetics.

For the study, reported in the American Journal of Human Genetics, the team examined the coding genes of three families that are not related to each other and are of different ancestry.

A total of eight relatives showed the typical symptoms of hair loss and had mutations in the LSS gene.

There is new hope for bald people to get back hair without going for transplantation as researchers have found that a drug originally developed to treat the bone disease, osteoporosis, stimulates hair growth.
However, the cholesterol blood values of those affected are not changed, the finsings showed, Pixabay

Using tissue samples, the scientists tried to find out exactly where the LSS is located in the hair follicle cells. The hair roots are formed in the follicle.

If the LSS gene is not mutated, the associated enzyme is located in a system of very fine channels in the follicle cells, the endoplasmic reticulum.

If a mutation is present, the lanosterol synthase also spreads outside these channels into the adjacent substance, the cytosol, the scientists observed.

“We are not yet able to say why the hair is falling out,” said lead author Maria-Teresa Romano, a doctoral student from the varsity.

“It is likely that the displacement of LSS from the endoplasmic reticulum results in a malfunction.”

Also Read- Managing Weight During Pregnancy May Affect Child’s Bone Health

“A better understanding of the causes of the disease may in future enable new approaches to the treatment of hair loss,” Romano said, adding that there is still a long way to go.

However, the discovery of the gene already contributes to an improved diagnosis of the rare disease. (IANS)