Preliminary definition of a “critical region” of chromosome 13 in q32: Report of 14 cases with 13q deletions and review of the literature

Abstract

We report on 14 patients with partial deletions of chromosome 13q. These patients exhibit a wide spectrum of phenotypes. Deletions limited to proximal bands q13-q31 are associated with growth retardation but not with major malformations. We review the literature since 1975 and summarize 13q deletion cases which have a phenotype involving one or more major malformations and mental retardation. Analysis of the breakpoints of these cases, as well as those reported by us, supports the hypothesis that only deletions involving at least part of band q32 are associated with major malformations and digital abnormalities. Patients with more distal deletions have severe mental retardation but do not have major malformations or growth retardation. A group of patients in whom the breakpoint is stated to be within q32 has had an intermediate phenotype. This suggests that it may be possible to define subregions within q32 whose deletion is associated with particular developmental defects.

Tyrosinase and related proteins in mammalian pigmentation

“…It is even possible that slaty and slaty-2J completely abolish TRP-2 activity, and that residual Dct activity is derived from other enzymes. In human, case studies of chromosomal deletions involving 13q31-q32 have not reported any apparent pigmentation abnormalities [46]. However, it is possible that TRP-2 protects the melanocyte against cytotoxicity of decarboxylated indolic melanogenic intermediates by limiting their formation.…”

The first Korean case of Waardenburg-Shah syndrome with novel endothelin receptor type B mutations

“…Tuysuz et al [9] reported variable features of WS IV associated with de novo heterozygous deletions involving chromosome 13q and including the EDNRB gene. The three patients had common facial features consistent with the proximal 13q deletion syndrome and mild developmental delay [12]. However, their clinical phenotypes including hypopigmentation of the irides, hearing loss, and Hirschsprung's disease were discordant between the patients' findings [9], which suggests that there are variable expressions observed in patients with heterozygous loss of function mutations in EDNRB.…”

Postnatal diagnosis of constitutive ring chromosome 13 using both conventional and molecular cytogenetic approaches

“…Brown et al (1993) defined 13q32 as the critical region for the most severe phenotypes, showing malformations in the brain, eyes, distal limbs, and genitourinary and gastrointestinal tracts, severe mental retardation, and short stature. The previous description is in agreement with our findings.…”