Found a gene responsible for walking on all fours
Turkish biologists have discovered a genetic mutation that prevents humans from learning to walk upright. This discovery will help to identify the evolutionary patterns that led to the fact that humans mastered walking on two legs, according to the message of the European Society of Human Genetics.
Several families, some of whom walked on all fours, were discovered in Turkey in 2005. For the first time this pathology was described by the Turkish scientist Uner Tan, who called this disease by his own name - Unertana syndrome.
In an article then published in the journal Neuroquantology, the scientist described a family in which five of 19 children “walked on two arms and two legs, with straight knees. They could get up, but only for a short time, with bent knees. They were distinguished by poor speech skills and mental retardation.
This case was considered as an example of reverse evolution - movement backward along the evolutionary ladder.
At the conference of the European Society of Human Genetics in Barcelona on Monday, the results of a genetic examination of those suffering from Unertana's syndrome, carried out by a group of scientists led by Professor Taifun Ozcelik from Bilkent University (Ankara), were presented.
The researchers found that members of two families, traveling on all fours, had a mutation in the gene responsible for the very low-density lipoprotein receptor. This protein is critical for the proper functioning of the cerebellum, one of the brain regions responsible for coordinating movements.
Although the families lived in isolated villages 200-300 kilometers apart and reportedly had no ancestors in common, scientists hoped to find a single genetic mutation associated with the condition. They were surprised to find that things were different.
“We performed genetic testing of these families and found areas in the DNA that are common to all family members who walk on all fours. However, we were surprised to find that genes on three different chromosomes are responsible for this disease in four different families,”says Professor Ozchelik.
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According to him, mutations in the gene responsible for VLDLR were found in families A and D, but such a mutation was not found in either family B or family C.
In all cases, all sufferers of Unertana's syndrome were descendants of closely related marriages. All of them had significant developmental delays in childhood.
“While normal children change to walking on two legs after a relatively short time, these people continued to walk on their hands and feet and never walked upright. Although they could get up from a sitting position with bent knees, they practically never walked on foot,”Ozchelik notes.
Previously it was assumed that the lack of access to medical care exacerbated the effect of delayed cerebellar development, which led to walking on all fours, RIA Novosti reports.
“Although it was true that family B did not have access to quality medical care, families A and D could go to doctors, and both families tried to cure their children with this syndrome,” says Ozchelik.
“One of family A is a physician who has been actively involved in medical interventions. In addition, parents in Family A also tried to wean their children from walking on all fours, but this did not work. We believe that social factors were not involved in the development of this syndrome,”adds the scientist.
VLDLR deficiency mutations have also been found in the Hatterite sect, a group of Anabaptists living in North America. Among those who were found to have this mutation, there were also many who did not possess upright walking skills. The neurological characteristics of members of Turkish families affected by Unertana's syndrome and among hatterites are similar. The biggest difference is that Turkish families can walk on all fours, scientists say.
They suggest that the mutation in hatterites may be much more pronounced, so much so that they are unable to walk even on all fours.
Along with the large size of the brain, speech, the ability to make tools, upright posture has long been considered one of the key features that led to the formation of modern man.
A group led by Professor Ozchelik has discovered how mutations in the gene responsible for the production of VLDLR affect brain development and motor abilities in humans.
“It is possible that the VLDLR gene is associated with other types of brain disorders. In addition, we hope to find defective genes associated with walking on all fours in families B and C,”says Ozchelik.