As we all know, we inherit half of our genes from our mothers and the other half from our fathers.For the function of most genes, it doesn't matter which parent the gene comes from.But this is not true for all genes: about 150 are affected by "genomic imprinting", meaning they are either active only when they inherit from their mother or are active only when they inherit from their father.Most of these "imprinted" genes are important for our development.

Simon Hippenmeyer, a professor at the Institute of Science and Technology of Austria (IST Austria), and his team, including Postdoc Susanne Laukoter and Senior laboratory technician Florian Pauler, have shown that brain cells react very differently to genome-specific imprinting, depending on the cell type.The results appear in the journal Neuron.

Previous studies have shown that imprinted genes are more active in some tissues and less active in others.The neuroscientists, led by Hippenmeyer, found that imprinted genes in the cortex were also more expressed, or more active, in some cell types and in some cell types.

To investigate the effects of this change in gene activity, the researchers used MADM technology established by Hippenmeyer.Susanne Laukoter explains, "This technique allows us to encode the color of cells while simultaneously increasing or decreasing the level of gene expression.In our experiment, we doubled the expression of imprinted genes in some cells and turned them off completely in others.So we were able to look at the response of cells at the single-cell level to changes in gene dose."

The researchers found that cells respond to changes in the dose of imprinted genes by activating certain genomes, particularly those important for cell death, growth, and synaptic formation.This response was strongest in the cell type of astrocytes, the glial cells that support neurons.Detailed analysis showed that some astrocytes given double doses of their paternal genes always had higher Numbers than those given double doses of their maternal genes.This difference exists throughout the development of the brain.Florian Pauler explains: "Genomic imprinting can protect cells from cell death by doubling the dose of the paternal gene, or accelerate cell death by doubling the dose of the maternal gene."

While earlier studies have shown a link between genomic imprinting and cell death, the newly published study now shows that the link depends on the cell type and is particularly strong in astrocytes.Neurons with dual maternal genes do not respond to changes in cell death, but form different connections and networks.Simon Hippenmeyer explains the results."Each cell type responds differently to dimorphism, which is the presence of two maternal or two paternal genes."It may also be important for humans."Prader-willi syndrome and Angelman syndrome are caused by duplication of imprinted chromosomal segments.Each organ responds differently to repetition.Hopefully, if we can better understand cell-type-specific responses, we may be able to target therapies in the future.

The study also solves a longstanding debate in the field of neurobiology about how many genes in the brain are imprinted by the genome, Hippenmeyer reports."There are dozens of genes imprinted in the cortex that significantly affect development."