So it does not appear, in general, that a child receiving both copies of region q28.3 of chromosome 4 from the same parent would cause a disorder. However …
PCDH10 = Gene encoding Protocadherin-10
ASD = Autism Spectrum Disorders
If both copies of the chromosome lack the PCDH10 gene (homozygous deletion), which is rare, then an autism spectrum disorder could possibly result.
A cadherin is a protein involved in certain types of cell-cell junctions: “cadherin” comes from “Calcium-dependent adhesion”. Cadherin proteins protrude out of the cell and attach to cadherin proteins projecting out of neighboring cells, thereby helping to hold cells together. To function, they require calcium (hence the calcium-dependent part). Here is a diagram showing a different cadherin involved in a cell-cell junction called an adherens junction
http://www.nature.com/nrc/journal/v4/n6/…
Protocadherin-10 is a specific type of cadherin; it is found in the brain, and helps form connections between brain cells
Axon = the long “tail” of a neuron (nerve cell) that sends signals to a receiving cell (such as another neuron). Here is a picture:
http://www.brainexplorer.org/brain-image…
Axon migration = the process by which axons grow in length and follow chemically defined paths to form synapses onto target cells (other neurons, muscle cells, glands, etc). In essence, neuron X sends out an axon and that axon feels it way around (sensing chemical gradients) and finds its way to neuron Y, and then forms a signaling connection called a synapse with Y.
So if there is a problem with PCDH10, the protocadherin-10 protein is defective (or absent) and axon migration will not function correctly – the brain will not wire itself correctly in certain regions, such as the forebrain. This will disrupt learning. Apparently, this is what would give rise to the autism spectrum disorder.
Recessive mutations = a change in DNA that requires both copies of the chromosome to have it in order for a noticeable difference (different phenotype) to occur