Making chromosome abnormalities treatable conditions

Evidence for common mechanisms of pathology between SHANK3 and other genes of Phelan-McDermid syndrome

Chromosome 22q13.3 deletion (Phelan-McDermid) syndrome (PMS, OMIM 606232) is a rare genetic condition that impacts neurodevelopment. PMS most commonly results from heterozygous contiguous gene deletions that include the SHANK3 gene or likely pathogenic variants of SHANK3 (PMS-SHANK3 related). Rarely, chromosomal rearrangements that spare SHANK3 share the same general phenotype (PMS-SHANK3 unrelated). Very recent human and model system studies of genes that likely contribute to the PMS phenotype point to overlap in gene functions associated with neurodevelopment, synaptic formation, stress/inflammation and regulation of gene expression. In this review of recent findings, we describe the functional overlaps between SHANK3 and six partner genes of 22q13.3 (PLXNB2, BRD1, CELSR1, PHF21B, SULT4A1, and TCF20), which suggest a model that explains the commonality between PMS-SHANK3 related and PMS-SHANK3 unrelated classes of PMS. These genes are likely not the only contributors to neurodevelopmental impairments in the region, but they are the best documented to date. The review provides evidence for the overlapping and likely synergistic contributions of these genes to the PMS phenotype.

A Peruvian Child with 18p-/18q+ Syndrome and Persistent Microscopic Hematuria

Chromosome 18 pericentric inversion carriers could have offspring with recombinant chromosomes, leading to patients with clinical variable manifestations. Patients with 18p-/18q+ rearrangements share some clinical characteristics, while other characteristics differ. Factors for such divergence include the length of the inverted segment, among others. Here, we describe a Peruvian child with dysmorphic features, intellectual disability persistent microscopic hematuria, aortic pseudocoarctation, and descending aorta arteritis, among others. Karyotype analysis of family members determined the mother as the carrier of a pericentric inversion: 18[inv(18)(p11.2q21.3)]. This child carries a recombinant chromosome 18, with chromosomal microarray analysis detecting two genomic imbalances in patient's chromosome 18: one duplicated region and one deleted segment in the large and the short arms, respectively. Persistent microscopic hematuria has not been reported among 18p-/18q+ phenotypes. Our patient elucidates that other factors play significant and yet unknown roles for not fulfilling the proposed genotype-phenotype correlation associated with hemizygosity in this type of recombinant chromosome 18 or presenting these features as the patient ages.