22q11 deletion syndrome: current perspective

Bülent Hacihamdioğlu,1 Duygu Hacihamdioğlu,2 Kenan Delil3 1Department of Pediatric Endocrinology, 2Department of Pediatric Nephrology, GATA Haydarpasa Training Hospital, 3Department of Medical Genetics, Marmara University, School of Medicine, Istanbul, Turkey Abstract: Chromosome 22q11 is characterized by the presence of chromosome-specific low-copy repeats or segmental duplications. This region of the chromosome is very unstable and susceptible to mutations. The misalignment of low-copy repeats during nonallelic homologous recombination leads to the deletion of the 22q11.2 region, which results in 22q11 deletion syndrome (22q11DS). The 22q11.2 deletion is associated with a wide variety of phenotypes. The term 22q11DS is an umbrella term that is used to encompass all 22q11.2 deletion-associated phenotypes. The haploinsufficiency of genes located at 22q11.2 affects the early morphogenesis of the pharyngeal arches, heart, skeleton, and brain. TBX1 is the most important gene for 22q11DS. This syndrome can ultimately affect many organs or systems; therefore, it has a very wide phenotypic spectrum. An increasing amount of information is available related to the pathogenesis, clinical phenotypes, and management of this syndrome in recent years. This review summarizes the current clinical and genetic status related to 22q11DS. Keywords: DiGeorge syndrome, velocardiofacial syndrome, TBX

22q11.2 rearrangements found in women with low ovarian reserve and premature ovarian insufficiency

International audienceOvarian reserve represents the number of available follicles/oocytes within ovaries and it can be assessed by follicle stimulating hormone levels, anti-Müllerian hormone levels, and/or antral follicle count determined by ultrasounds. A low ovarian reserve is defined by an abnormal ovarian reserve test. This condition can be considered premature if it occurs before the age of 40, leading to premature ovarian insufficiency. Despite the growing knowledge concerning the genetic basis of ovarian deficiency, the majority of cases remain without a genetic diagnosis. Although 22q11.2 deletions and duplications have been associated with genitourinary malformations, ovarian deficiency is not a commonly reported feature. We report here four patients bearing a 22q11.2 rearrangement, identified during the clinical assessment of their low ovarian reserve or premature ovarian insufficiency, and discuss the molecular basis of the ovarian defects