(ORDO NEWS) — Congenital absence of the nose, or arynia, is an extremely rare developmental anomaly: less than a hundred such cases have been described throughout history.
A new study has established the genetic basis of aronia, namely the role of SMCHD1 gene knockout and associated DUX4 gene activation.
Among the many congenital anomalies arising from disorders of embryonic development, there are many rare and very rare.
However, aronia, that is, the absence of a nose from birth, stands out even among them.
Since the first description in 1931, doctors have noted only a few dozen people (no more than a hundred) who were born without a nose.
Such an anomaly means the absence of not only an important part of the face, but also the sinuses, olfactory epithelium and some other defects, including the eyes.
Children born with arynia need urgent help and in the future – in the supervision of doctors.
Trying to find the molecular genetic causes of birth without a nose, scientists turned their attention to the SMCHD1 gene.
It is known that mutations in it also cause another congenital anomaly – humeroscapular-facial muscular dystrophy, which manifests itself in a completely different way.
Its authors used cells obtained from patients with arynia, as well as cultures of normal human embryonic cells in which the SMCHD1 gene was knocked out.
To begin with, scientists stimulated their transformation into tissues, from which the olfactory epithelium and other structures normally develop in the embryo.
As expected, the breakdown of SMCHD1 prevented embryonic cells from normal differentiation. Moreover, scientists noted in them signs of apoptosis – programmed cell death.
In addition, such cells have lost the ability to group into clusters that are present in the tissues of a normal embryo.
It also turned out that switching off the SMCHD1 gene is accompanied by an increase in the activity of another gene, DUX4.
It codes for one of the transcription factors, special proteins that regulate the process of “rewriting” DNA into the form of RNA.
This interaction of genes is associated, among other things, with DNA methylation, an important mechanism of epigenetic regulation.
At the same time, the return of the activity of the SMCHD1 gene , as well as the suppression of DUX4 expression, allowed the cells to develop normally.
This proves that both genes are of key importance for the development of pathological changes leading to congenital absence of the nose.
It is also significant that the authors considered the role of external factors in the development of this seemingly purely genetic disease.
It turned out that infection of cells with the herpes virus type 1 enhances the expression of DUX4 and also stimulates pathological changes in cells carrying mutations that cause aronia.
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