Interstitial deletion of the long arm of chromosome 2: a dose study on isocitrate dehydrogenase 1

Small deletions of SATB2 cause some of the clinical features of the 2q33.1 microdeletion syndrome

Recurrent deletions of 2q32q33 have recently been reported as a new microdeletion syndrome. Clinical features of this syndrome include severe mental retardation, growth retardation, dysmorphic features, thin and sparse hair, feeding difficulties and cleft or high palate. The commonly deleted region contains at least seven genes. Haploinsufficiency of one of these genes, SATB2, a DNA-binding protein that regulates gene expression, has been implicated as causative in the cleft or high palate of individuals with 2q32q33 microdeletion syndrome. In this study we describe three individuals with smaller microdeletions of this region, within 2q33.1. The deletions ranged in size from 173.1 kb to 185.2 kb and spanned part of SATB2. Review of clinical records showed similar clinical features among these individuals, including severe developmental delay and tooth abnormalities. Two of the individuals had behavioral problems. Only one of the subjects presented here had a cleft palate, suggesting reduced penetrance for this feature. Our results suggest that deletion of SATB2 is responsible for several of the clinical features associated with 2q32q33 microdeletion syndrome.

Distal deletion, del(2)(q33.3q33.3), in a patient with severe growth deficiency and minor anomalies

We report on an 18-month-old boy with a 2q33.3 deletion. The clinical findings observed in the propositus included minor anomalies of face and distal limbs, intrauterine and postnatal growth retardation, microcephaly and, so far, moderate developmental delay. Conventional GTG banded chromosome analysis indicated a small deletion in distal 2q. Subsequent analysis by fluorescent in situ hybridization (FISH) using different probes allowed us to narrow down the deletion to most or all of segment 2q33.3. This case shows the importance of the application of different YAC probes for a precise determination of breakpoints in small interstitial deletions.

Two cases with interstitial deletions of chromosome 2 and sex reversal in one

We present two children with de novo interstitial deletions of the long arm of chromosome 2 (karyotypes 46,XY, del(2)(q31.1q31.3) and 46,XY, del(2)(q24.3q31.3), respectively). The first child had severe learning difficulties, growth retardation, unilateral ptosis, small palpebral fissures, a cleft uvula, and bilateral cutaneous syndactyly of the second and third toes. Despite her male karyotype, she had female external genitalia with hypoplasia of the clitoris and labia minora. This is the first reported case of feminization of the external genitalia in a genotypic male with an interstitial deletion of chromosome 2q31 and adds to the growing amount of evidence for a gene involved in sex determination in this chromosome region. The second child had severe mental and growth retardation, ptosis, down-slanting palpebral fissures, low-set ears, micrognathia, finger camptodactyly, and brachysyndactyly of the second to fifth toes. The clinical manifestations associated with deletions of 2q31 to 2q33 are similar to those found with proximal deletions at 2q24 to 2q31 and of band 2q24, suggesting that the phenotype may result from haploinsufficiency for one or more genes located at 2q31. Microsatellite marker studies showed that both children had paternally derived deletions that included the HOXD gene cluster and the EVX2, DLX1, and DLX2 genes known to be important in limb development.