Cytogenetic abnormalities, which may include chromosomal trisomy (such as Down syndrome), mosaicism, or rearrangements, such as deletions or duplications, cause a significant proportion of cognitive impairment and morbidity and mortality, especially among infants and children.
Advances in high-resolution cytogenomic analysis and the development of the molecular cytogenetics field, mainly through the application of fluorescence in situ hybridization and array-comparative genomic hybridization (CGH; also known as cytogenomic microarray analysis or CMA), provide opportunities for identifying subtle chromosomal rearrangements, such as cryptic deletions or duplications, in individuals with IDD or genetic syndromes.
The application of massively parallel, high throughput next generation sequencing (NGS) has revolutionized many aspects of research and clinical medicine. The ability to analyze the whole exomes (expressed genes) or whole genomes (all of the genetic material of a person, tissue, or cell type) has allowed an unprecedented window into human health and disease. In the field of IDD, genomic approaches are being used for diagnosis when a clear genetic syndrome or genetic cause has not previously been identified, with the potential to uncover many new genes implicated in human neurodevelopment and neurological function. Other genetic conditions may be caused by mutations that affect epigenetic mechanisms (resulting from changes in the regulation of gene activity and expression not dependent on gene sequence) or somatic mutations (mutations only found in specific affected tissues).
Studies of genetics, genomics, and epigenetics are a core portion of the IDDB portfolio and represent exciting new areas of research for the NICHD.