This gene is carried on the X chromosome, so females have two copies of the gene and males only one.
Debra Silver, PhD, associate professor of molecular genetics and microbiology at Duke School of Medicine, said: “If you remove both copies of the gene in female mice, that leads to giant microcephaly. where the brain is severely reduced in size. who led the research team. “But removing a copy could more closely mimic what’s happening in human patients,” Silver said.
In other words, the defects caused by defective DDX3X are dose-dependent – the syndrome can vary depending on how affected the production of helicases is caused by the mutation. Findings appear in an open access journal eLife.
Inheritance of neurodegeneration
When DDX3X is altered by a mutation during early development, “you don’t get as many neurons over time as this gene is needed to produce neurons from other cells,” Silver said. precursor cells”. “And it is also helping the seniors to divide properly.”
If neural progenitor cells normally take 15 hours or longer to divide, a mutant DDX3X could make that process even longer, Silver said. “And that means that over time, if these neural precursors take too long to divide, then you fall behind and the brain doesn’t develop properly.”
In an earlier study the team published in March 2020, using genetic samples from 107 children with developmental disabilities around the world, researchers found that half of the DDX3X mutations had disrupts the gene completely, but the other half just makes it work less.
The children in the previous study were mostly female, leading the researchers to suggest that loss of DDX3X in males would be fatal, since they carried only a single copy of the gene. But in this study, Silver’s team found that a male Y-chromosome companion gene, DDX3Y, can perform some of the gene’s functions. She said.
Some RNAs with reduced translational capacity due to damage caused by DDX3X also play a role in brain development, Silver said. “So it helped us discover what I call this network of RNAs where translation depends on this gene. And it started to give us clues as to where DDX3X might be disrupting. how the brain develops.”
DDX3X is also implicated in neurodegeneration, some cancer progression, and innate immune responses. Silver says understanding the cellular processes and molecular targets of DDX3X in the developing brain could help shed light on the basis of many disorders.
“We know of more than 800 families worldwide who have been diagnosed with DDX3X syndrome,” says Silver. “This is certainly an important gene, with possibly hundreds of mutations. There’s really a lot to learn about how DDX3X controls brain development.”
“We hope this study can improve our understanding of the basis for DDX3X syndrome and related disorders,” Silver said. “In the long run, this could help contribute to the development of therapies.”