Inverted duplications deletions: underdiagnosed rearrangements??

Abstract

Molecular techniques led to the discovery that several chromosome rearrangements interpreted as terminal duplications were in fact inverted duplications contiguous to terminal deletions. Inv dup del rearrangements originate through a symmetric dicentric chromosome that, after asymmetric breakage, generates an inv dup del and a deleted chromosome. In recurrent inverted duplications the dicentric chromosome is formed at meiosis through non-allelic homologous recombination. In non-recurrent inv dup del cases, dicentric intermediates are formed by non-homologous end joining or intrastrand annealing. Some authors hypothesized that in these cases the dicentric may have been formed directly in the zygote. Healing of the broken dicentric chromosomes can occur not only in a telomerase-dependent way but also through telomere capture and circularization thus creating translocated or ring inv dup del chromosomes. In all the cases reported up to now, the duplicated region was always longer than the deleted one, but we can safely assume that there is another group of rearrangements where the deleted region is longer than the duplicated portion. In general, in these cases, the cytogeneticist will suspect the presence of a deletion and confirm it by FISH with a subtelomeric probe, but he/she will almost certainly miss the duplication. It is likely that the conventional analysis techniques used until now have led to a substantial underestimate of the frequency of inv dup del rearrangements and that the widespread use of array-CGH in routine analysis will allow a more realistic estimate. Obviously, the concomitant presence of deletion and duplication has important consequences in genotype/phenotype correlations.

Citation

The Project 8p Foundation (Project 8p) was created in 2018 to:

  • Accelerate future treatments, not only for 8p, but potentially for other chromosome-wide diseases as well.
  • Lead with knowledge from patients. Currently, there is no cure for 8p disorders, nor is there a standard course of treatment.

The Project 8p Foundation (Project 8p) was created in 2018 to:

  • Raise transformative funding for pioneering scientific research into treatments for a complex, rare disease involving 250+ affected genes on the short arm of the 8 th chromosome (8p). Rearrangements of these genes causes significant abnormalities to the entire neurological system, thus all organs and functions of the body– with variance in cognitive functions, gross motor skills, social development and other challenges during infancy, and throughout life;
  • Empower a unified community of 8p patients and their families so they can have meaningful lives today; and
  • Accelerate future treatments, not only for 8p, but potentially for other chromosome-wide diseases as well.