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Mammals’chromosomeshave a vast influence over whether an individual develops as manful or female — but a new study reveals that the pull of these sex chromosome can be overridden by bantam molecules foretell microRNAs .
The study , published May 7 in the journalNature Communications , showed that deleting the factor behind specific microRNAs could transform manly computer mouse into female in the womb , sparking a complete sex reversal .
The X and Y chromosomes aren’t the only factors that determine biological sex, a new study highlights.
" We did not expect that the results would be as striking as they are , " study co - authorRafael Jiménez , a professor of genetic science at the University of Granada , told Live Science .
Sex determination in mammalsrelies on a ok balance between " opposite " set of factor — one that drives the ontogenesis of female characteristics , such as ovaries , and another that get virile feature , such as nut . Early in an animal ’s development , the scale tip one agency or another , leading to an irreversible cascade of step that ends in the growing of either set of sex activity organs .
" In a very other stagecoach of our developing , all the mammals have the content of being virile or distaff , potentially , " say study co - authorFrancisco Barrionuevo , a prof of genetics at the University of Granada .
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A gene called SRY , which is only incur on the Y chromosome , triggers the serial publication of events that form testes . The gene ’s absence seizure in individuals with only X chromosome results in the establishment of ovaries . Scientists know a groovy deal about the factor involved in making the protein ask for these cognitive operation . But a huge share of mammal ' DNA — including about 98 % of the human genome — does n’t code for any proteins , so scientist were timid what theatrical role these other factor play in sex conclusion , if any .
Long considered"junk DNA,“these stretch of genetic material are converted into mote called non - codingRNA , rather than proteins . The RNA can dissemble many biologic processes . About one - quartern of these molecules are microRNAs , which can attach to numerous genes and regulate their activity levels .
Out of thousands of sleep together microRNAs , the squad focused on a group of six known to interact with genes involved in sex decision . They edit these speck from growing mouse foetus that had either XY or XX chromosome . The XX mice developed ovaries , as expect , but the XY shiner showed early sign of spring up uterus and had ovaries indistinguishable from those in XX mice .
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" We saw the sex gland [ under the microscope ] and it was full of the signal for this female marker,“Alicia Hurtado , first author of the study and a postdoctoral researcher at the Andalusian Center for Development Biology in Seville , say Live Science . To confirm the results , they retell the experiments multiple times , using dissimilar strategies to cancel the microRNAs .
For orchis to grow the right way in XY animals , the protein made by the SRY cistron must be made in the appropriate amount and at the right time . The absence of the six microRNAs in XY mouse caused this protein to be made about 12 hour later on than normal , the investigator found . This , in bit , impacted the yield of a different protein that ’s essential for the growth of male sex organs . Ultimately , this chain of upshot conduct to the mouse ’s sex reverse .
" [ These finding ] fit very well with what we know , except it brings another level of complexity , " saidSerge Nef , a prof of transmitted medicine and development at the University of Geneva who was not involved in the study . " It is one extra brick in our reason of the whole [ sex decision ] process in mammalian , " he say Live Science .
While the study has only been done in mice , the six key microRNAs are found in all vertebrates and date back to the first vertebrate , about 500 million years ago . Therefore , it is very likely that this cluster of microRNAs works likewise in other mammals , as well — including humans .
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