Delayed Neuropsychomotor Development and Seizures in a Patient with Ring Chromosome 20 – Candidate Genes
Ring chromosomes are rare chromosomal abnormalities in which the long arm of the
chromosome has been fused with the short arm. This often results in deletions and
duplications of the chromosome. Ring Chromosome 20 (r20) is a syndrome characterized
by refractory epilepsy, intellectual disability, and behavioral disorders.
In this article, the authors report on a two-year-old female patient with nonmosaic ring
chromosome 20 and duplications and deletions in 20q13.33. The patient’s clinical
characteristics included epilepsy, delayed motor and language development, and
cognitive deficits. However, there are very few r20 individuals with 20q13.33 deletions
and their clinical presentations vary broadly. The implications of the ring morphology are
unknown, as well as the significance of the deletions within this context. Utilizing
chromosomal microarray analysis (CMA) and protein-protein interaction data the authors
were able to identify candidate genes in the deleted region that might help explain the r20
20q13.33 disease phenotype.
The proteins ARFGAP1, HELZ2, COL9A3, PTK6, and EEF1A2 were identified as hubs that
have a central function in a biological network. Bottlenecks in the network were defined
as genes that were related to control of information between the interactions in the
network. The authors identified that haploinsufficiency of the genes identified as
bottlenecks (CHRNA4, ARFRP1, GID8, COL9A3, PTK6, ZBTB46, and SRMS) could
contribute to pathophysiology of r20 20q13.33. Additionally, genes PTK6 and COL9A3
were identified as having high betweenness scores as they are crucial to the information
flow in the network and represent critical points of the network.
The authors conclude that these candidate genes, which are related to biological
processes that include nucleosome assembly, DNA repair, and cholinergic synaptic
transmission, could be associated with the clinical characteristics of r20 20q13.33
patients. However, the authors do note that the circular conformation and 20q13.33
duplications could limit genotype-phenotype correlations.
Corrêa, Thiago, et al. “Candidate Genes Associated with Delayed Neuropsychomotor
Development and Seizures in a Patient with Ring Chromosome 20.” Case Reports in
Genetics, vol. 2020, 2020, pp. 1–6., doi:10.1155/2020/5957415.
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