Melanie Babcock

Microduplication and triplication of 22q11.2: a highly variable syndrome.

22q11.2 microduplications of a 3-Mb region surrounded by low-copy repeats should be, theoretically, as frequent as the deletions of this region; however, few microduplications have been reported. We show that the phenotype of these patients with microduplications is extremely diverse, ranging from normal to behavioral abnormalities to multiple defects, only some of which are reminiscent of the 22q11.2 deletion syndrome. This diversity will make ascertainment difficult and will necessitate a rapid-screening method. We demonstrate the utility of four different screening methods. Although all the screening techniques give unique information, the efficiency of real-time polymerase chain reaction allowed the discovery of two 22q11.2 microduplications in a series of 275 females who tested negative for fragile X syndrome, thus widening the phenotypic diversity. Ascertainment of the fragile X-negative cohort was twice that of the cohort screened for the 22q11.2 deletion. We also report the first patient with a 22q11.2 triplication and show that this patients mother carries a 22q11.2 microduplication. We strongly recommend that other family members of patients with 22q11.2 microduplications also be tested, since we found several phenotypically normal parents who were carriers of the chromosomal abnormality.

GJB2 mutation spectrum in 209 hearing impaired individuals of predominantly Caribbean Hispanic and African descent

OBJECTIVE The purpose of the study is to determine whether Caribbean Hispanic and African admixture populations have a paucity of mutations in GJB2, encoding connexin 26. METHODS We reported the paucity of mutations in GJB2 and deletions in GJB6 in Caribbean Hispanic and African admixture populations in the Bronx, NY, in 2007 [1]. We have now collected 102 additional probands with non-syndromic sensorineural hearing impairment (NSHI), for a total of 209. We describe here a presentation of the combined data. RESULTS Of the 209 probands, 36% have affected family members with NSHI and the rest have sporadic occurrence. Of the familial cases, 43% had a first-degree relative affected, and the remainder a more distant relative. The hearing impairment ranged from unilateral mild to bilateral profound, with 76% exhibiting bilateral NSHI (BLNSHI). The single coding exon of the GJB2 gene was sequenced in 209 probands, PCR screening for del(GJB6-D13S1830) and sequencing of the non-coding exon of GJB2 to look for the known splice site mutation was performed in 32 NSHI patients with a heterozygous variation in GJB2, and multiplex ligation-dependent probe amplification (MLPA) testing of GJB2 and GJB6 exon deletions or amplifications (P163 GJB-WFS1 kit) was done in 70 probands. Eight unrelated individuals had biallelic GJB2 mutations, representing 4% of our entire cohort, or 5% of our probands with BLNSHI. Of 127 probands of Hispanic or African descent with BLNSHI, six (4.7%) had biallelic pathogenic mutations, three (2.3%) had monoallelic mutations and 118 (93%) had no disease-causing mutations in GJB2. At the same time, no major deletions were identified either by PCR screening (del(GJB6-D13S1830)) or by MLPA analysis (GJB2 or GJB6), and no subjects had the known splice site mutation in GJB2. CONCLUSION These results demonstrate that GJB2 is not the major contributor to the genetic basis of NSHI for the Bronx minority admixture populations.

Spectrum of elastin sequence variants and cardiovascular phenotypes in 49 patients with Williams–Beuren syndrome†

Haploinsufficiency of the elastin gene (ELN) on 7q11.23 is responsible for supravalvular aortic stenosis (SVAS) and other arteriopathies in patients with Williams–Beuren syndrome (WBS). These defects occur with variable penetrance and expressivity, but the basis of this is unknown. To determine whether DNA variations in ELN could serve as genetic modifiers, we sequenced the 33 exons and immediately surrounding sequence of the ELN gene (9,455 bp of sequence) in 49 DNAs from patients with WBS and compared cardiovascular phenotypes. Four missense, and four novel intronic variants were identified from a total of 24 mostly intronic single nucleotide variations and one indel. Two missense changes were present in one patient each, one published, p.Gly610Ser in exon 27 (MAF, 0.003) and one novel, p.Cys714Tyr, in exon 33 (MAF, 0.001), were rare in the general population. To identify a statistical association between the variants identified here and cardiovascular phenotypes a larger cohort would be needed.

Molecular characterization of an interstitial deletion of 1p31.3 in a patient with obesity and psychiatric illness and a review of the literature

We report on the clinical and array‐based characterization of an interstitial 1p31.3 deletion in a 15‐year‐old male patient with obesity, behavioral problems including multiple psychiatric diagnoses, mild intellectual impairment, facial dysmorphism, and a strong family history of psychiatric illness. The deletion breakpoints were determined by molecular karyotyping, revealing a 3.2 Mb excision. Patients previously reported with hemizygous deletions including this cytogenetic band had intellectual impairment and some facial features that overlap with our patients phenotype. However, their deletions were larger, encompassing several cytogenetic bands, making this case the smallest deletion to date that we are aware of sharing these phenotypic characteristics. There are 17 genes that map to the interval. Two genes within the interval, LEPR and PDE4B, are interesting candidates for these phenotypes because of their potential role in obesity and psychiatric illness, respectively. Identification of the smaller deletion underscores the importance of combining clinical investigation and array comparative genomic hybridization analysis for appropriate diagnosis, genetic counseling and potentially for prenatal diagnosis.

Dextrocardia, atrial septal defect, severe developmental delay, facial anomalies, and supernumerary ribs in a child with a complex unbalanced 8;22 translocation including partial 8p duplication.

We report on a child with dextrocardia, atrial septal defect (ASD), severe developmental delay, hypotonia, 13 pairs of ribs, left preauricular choristoma, hirsutism, and craniofacial abnormalities. Prenatal cytogenetic evaluation showed karyotype 46,XY,?dup(8p)ish del(8)pter. Postnatal array CGH demonstrated a 6.8 Mb terminal deletion at 8p23.3–p23, an interstitial 31.1 Mb duplication within 8p23.1–p11, and a terminal duplication of 0.24 Mb at 22q13.33, refining the karyotype to 46,XY,der(8)dup(8)(p23.1p11.1)t(8;22)(p23.1;q13.1).ish der(8)dup(8)(p23.1p11.1)t(8;22)(p23.1;q13.1) (D8S504‐,MS607 + ,ARSA + ,D8Z1 + , RP115713 + +). Previous reports of distal 8p deletion, 8p duplication, and distal 22q duplication have shown similar manifestations, including congenital heart disease, intellectual impairment, and multiple minor anomalies. We correlate the patients clinical findings with these particular areas of copy number. This case study supports the use of aCGH to identify subtle chromosomal rearrangement in infants with cardiac malformation as their most significant or only apparent birth defect. Additionally, it illustrates why aCGH is essential in the description of chromosome rearrangements, even those seemingly visible via routine karyotype. This method shows that there is often greater complexity submicroscopically, essential to an adequate understanding of a patients genotype and phenotype.

Interstitial duplication of 22q13.2 in a girl with short stature, impaired speech and language, and dysmorphism

The 22q13.3 deletion syndrome has been widely reported, with a known phenotype including global developmental delay, normal to accelerated growth and a characteristic facial appearance. A duplication syndrome involving this region has also been reported, with a somewhat more variable phenotype including psychomotor retardation, growth restriction, characteristic facial appearance differing from that seen in the deletion syndrome, and multiple malformations. The majority of reported patients have terminal duplications, with only three previous reports of interstitial duplication of the region. Herein we report a young woman with a de novo 569 kb interstitial duplication of 22q13.2 and short stature, speech and language impairment, refractive amblyopia, menorrhagia and facial dysmorphism. Comparison of her phenotype to previously reported patients with interstitial duplications reveals common traits including growth restriction, craniofacial anomalies and developmental delays. Included in the duplicated region is the gene EP300, mutations and deletions of which are implicated in Rubinstein-Taybi syndrome and thyrotroph embryonic factor, which has been proposed to be related to the pituitary hypoplasia seen in one patient with a large duplication, and several other genes without clear relation to disease.