During evolution, new types of cells emerge and perform new functions, resulting in changes in animals. Scientists study the origin and development of these new cell types to understand how they affect the animal’s bodily functions, structure, or behavior.
Scientists previously Mammalian ancestors Mammals live solitary lives, and parental care of young has developed over time in some mammalian groups. A research team led by scientists from Columbia University in New York recently used two closely related mouse species to elucidate how parental care evolved in mammals. The first species, the Asian goshawk, is monogamous and displays strong parenting behaviors, including grooming, herding, and retrieving young that have strayed from their nests. The second species, the deer mouse, is promiscuous and does not display parenting behaviors. The researchers aimed to investigate the genetic drivers of parental care in Asian goshawks.
They performed their experiments on two small clusters of cells located in the top part of each kidney. Adrenal glands These glands produce fat hormones, Steroid hormones Once produced, it immediately affects bodily function. The researchers found that the adrenal glands of monogamous Oldfield mice were six times heavier than those of promiscuous deer mice, an unexpectedly large size difference for such closely related species. When the researchers examined the tissue composition of both glands, they realized that the larger adrenal glands of Oldfield mice were due to larger and more numerous adrenal cells.
To look for molecular differences between the adrenal glands of the two mouse strains, the team studied the RNA molecules in their glands. RNA molecules copy genetic instructions from DNA and carry out the functions of genes. By counting and comparing the types and amounts of RNA molecules in the adrenal glands, the scientists hoped to understand how the adrenal glands functioned differently. They took adrenal tissue from adult mice, broke it down to release the RNA, and counted that RNA. They looked for differences in the amount of RNA, called ribosomal RNA. Akrc18 This level was 3,200 times higher in Oldfield mice than in deer mice, a difference that led the researchers to wonder whether this RNA might be related to the parental behavior seen in Oldfield mice.
The researchers, Akrc18 It produces steroid hormones. Steroid hormones affect parental behavior, so the team tested whether the hormone had an effect on mice. They gave Oldfield mice a single dose of the hormone and measured their parental behavior 20 hours later. They observed that these mice groomed and cuddled their pups longer, brought them back to their nests more frequently, and built stronger nests. In deer mice, which don’t normally show parental behavior, 17% of the injected mice groomed and brought back their pups. From these results, the scientists concluded that the hormone shapes the parental behavior of Oldfield mice.
The researchers also explained that mate bonding is an important aspect of monogamy. To understand partner choice, the researchers measured how long mice huddled with their partners compared to opposite-sex mice of the same species. They found that monogamous Oldfield mice huddled three times longer with their partners than with new individuals, whereas promiscuous deer mice huddled neither with their partners nor with strangers. Injecting the Akrc18 steroid hormone did not change these preferences, suggesting that the hormone only affected parenting behavior and not pair bonding.
The research team found that Oldfield mice had larger adrenal glands and that Akrc18 RNA production was related. To test whether the adrenal glands of the two mouse species had different cell types, the researchers used the RNA from the adrenal glands of both mice that they had previously counted. They used computational methods to search for specific RNAs in the cells and identify what cell types were present. They found that nearly all cell types were shared between the two species, except for one type that was present in Oldfield mice but not in deer mice.
Also, Akrc18 RNA was the most abundant element in these new cells. The researchers examined the structure and composition of the tissue and observed these cells lining the adrenal glands of wolf mice, which are absent in deer mice. The researchers suggested that these cell types may have evolved from existing adrenal cells by increasing production of steroid hormones and related genes. The researchers concluded that the parenting behavior of wolf mice is linked to this new type of cell in the adrenal glands.
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