NIPA1 and Angelman syndrome: The four non-imprinted biallelically expressed genes (TUBGCP5, CFYIP1, NIPA1, NIPA2) in this microdeletion were initially noted to impact severity of clinical presentation and neurological impairment in two classical genomic imprinting disorders (i.e., Prader-Willi and Angelman syndromes) with typical 15q11–q13 deletions depending on the absence or presence of the genomic area between breakpoints BP1 and BP2 containing the four genes leading to studies recognizing this syndrome.