The majority (99%) of individuals with 22q11.2 deletion syndrome (22q11.2DS) have a deletion that is caused by non-allelic homologous recombination between two of four low copy repeat clusters on chromosome 22q11.2 (LCR22s). However, in a small subset of patients, atypical deletions are observed with at least one deletion breakpoint within unique sequence between the LCR22s. The position of the chromosome breakpoints and the mechanisms driving those atypical deletions remain poorly studied. Our large-scale, whole genome sequencing study of >1500 subjects with 22q11.2DS identified six unrelated individuals with atypical deletions of different types. Using a combination of whole genome sequencing data and fiber-fluorescence in situ hybridization, we mapped the rearranged alleles in these subjects. In four of them, the distal breakpoints mapped within one of the LCR22s and we found that the deletions likely occurred by replication-based mechanisms. Interestingly, in two of them, an inversion probably preceded inter-chromosomal ‘allelic’ homologous recombination between differently oriented LCR22-D alleles. Inversion associated allelic homologous recombination (AHR) may well be a common mechanism driving (atypical) deletions on 22q11.2.
1. Carnivores are often food and/or macronutrient limited in their natural habitats, but whether they are limited mostly by protein or lipid is still a matter of controversy. As many predators and carnivorous scavengers also include plant material in their diet (omnivory), carbohydrate limitation is also possible.2. The authors used a recently described double-test procedure to test for food and macronutrient limitation in five co-existing species of predators and omnivorous scavengers from Uruguay (two crickets: Gryllus sp. and Miogryllus verticalis; two cockroaches: Blatta orientalis and Blaptica dubia and a harvestman: Acanthopachylus aculeatus).3. The authors found that the two crickets and one cockroach were food limited and one cockroach was non-protein (lipid) limited in the field. The harvestman showed a dramatic change in food limitation between two dates separated by only 3 weeks, but was non-protein (lipid) limited over both dates. From all species, the harvestman showed the highest self-selected intake of carbohydrates (27%), indicating a high level of omnivory. In contrast, the two cockroaches selected a surprisingly low proportion of carbohydrates (13-14%), while the crickets were intermediate (14-19%). The authors hypothesize that these omnivores are more carnivorous in the wild than expected from studies of laboratory populations.4. Though individuals were collected from the same habitats and all species self-selected macronutrient ratios characteristic of omnivorous carnivores, they showed different patterns of food and macronutrient limitation, reflecting species' niche segregation and individual differences in foraging success.
There is a controversy regarding how many species the genus Lagothrix contains, since the Lagothrix lagothricha subspecies have been recently proposed to be actual species. Clarification of species status is of particular importance in the case of L. l. lugens, because it is the most endangered and its distribution is restricted to the Colombian Andes, a highly deforested region. Using cytogenetic and molecular markers, we obtained evidence indicating that the subspecies status is appropriate for the two taxa occurring in this country. We also report high levels of intraspecific variability in the karyotype. We find evidence for a late Pleistocene separation of the subspecies, and we propose it is the limited area of contact between the taxa that allowed for them to partially differentiate.
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