Jane Hurst

Discovery of previously unidentified genomic disorders from the duplication architecture of the human genome

Genomic disorders are characterized by the presence of flanking segmental duplications that predispose these regions to recurrent rearrangement. Based on the duplication architecture of the genome, we investigated 130 regions that we hypothesized as candidates for previously undescribed genomic disorders. We tested 290 individuals with mental retardation by BAC array comparative genomic hybridization and identified 16 pathogenic rearrangements, including de novo microdeletions of 17q21.31 found in four individuals. Using oligonucleotide arrays, we refined the breakpoints of this microdeletion, defining a 478-kb critical region containing six genes that were deleted in all four individuals. We mapped the breakpoints of this deletion and of four other pathogenic rearrangements in 1q21.1, 15q13, 15q24 and 17q12 to flanking segmental duplications, suggesting that these are also sites of recurrent rearrangement. In common with the 17q21.31 deletion, these breakpoint regions are sites of copy number polymorphism in controls, indicating that these may be inherently unstable genomic regions.

Clinical and molecular delineation of the 17q21.31 microdeletion syndrome

Background: The chromosome 17q21.31 microdeletion syndrome is a novel genomic disorder that has originally been identified using high resolution genome analyses in patients with unexplained mental retardation. Aim: We report the molecular and/or clinical characterisation of 22 individuals with the 17q21.31 microdeletion syndrome. Results: We estimate the prevalence of the syndrome to be 1 in 16u2009000 and show that it is highly underdiagnosed. Extensive clinical examination reveals that developmental delay, hypotonia, facial dysmorphisms including a long face, a tubular or pear-shaped nose and a bulbous nasal tip, and a friendly/amiable behaviour are the most characteristic features. Other clinically important features include epilepsy, heart defects and kidney/urologic anomalies. Using high resolution oligonucleotide arrays we narrow the 17q21.31 critical region to a 424 kb genomic segment (chr17: 41046729–41470954, hg17) encompassing at least six genes, among which is the gene encoding microtubule associated protein tau (MAPT). Mutation screening of MAPT in 122 individuals with a phenotype suggestive of 17q21.31 deletion carriers, but who do not carry the recurrent deletion, failed to identify any disease associated variants. In five deletion carriers we identify a <500 bp rearrangement hotspot at the proximal breakpoint contained within an L2 LINE motif and show that in every case examined the parent originating the deletion carries a common 900 kb 17q21.31 inversion polymorphism, indicating that this inversion is a necessary factor for deletion to occur (p<10−5). Conclusion: Our data establish the 17q21.31 microdeletion syndrome as a clinically and molecularly well recognisable genomic disorder.

Molecular characterisation of patients with subtelomeric 22q abnormalities using chromosome specific array-based comparative genomic hybridisation.

The 22q13 deletion syndrome is associated with global developmental delay, absent or delayed speech, and generalised hypotonia. In this study, the size and nature of 22q13 deletions (n=9) were studied in detail by high-resolution chromosome specific array-based comparative genomic hybridisation (array CGH). The deletion sizes varied considerably between the different patients, that is, the largest deletion spanning 8.4u2009Mb with the breakpoint mapping to 22q13.2 and the smallest deletion spanning 3.3u2009Mb with the breakpoint mapping to 22q13.31. In one case, a unique subtelomeric 3.9u2009Mb deletion associated with a 2.0u2009Mb duplication of 22q13 was observed, adding to a growing number of similar cases identified for other chromosome ends. Remarkably, this patient had signs suggestive of retinitis pigmentosa, which has never been reported before in the 22q13 deletion syndrome. The identification of two pairs of recurrent proximal breakpoints on 22q13 suggests that these specific regions may be prone to recombination, due to yet unknown genome architectural features. In addition to the copy number changes on 22q13, a duplication of ∼330u2009kb on 22q11.1 was observed and shown to be a genetic large-scale copy number variation without clinical consequences. The current study failed to reveal relationships between the clinical features and the deletion sizes. Global developmental delay and absent or severely delayed speech were observed in all patients, whereas hypotonia was present in 89% of the cases (8/9). This study underscores the utility of array CGH for characterising the size and nature of subtelomeric deletions, such as monosomy 22q13, and underlines the considerable variability in deletion size in the 22q13 deletion syndrome regardless of the clinical phenotype.

“What is this Genetics, Anyway?” Understandings of Genetics, Illness Causality and Inheritance Among British Pakistani Users of Genetic Services

Misconceptions about basic genetic concepts and inheritance patterns may be widespread in the general population. This paper investigates understandings of genetics, illness causality and inheritance among British Pakistanis referred to a UK genetics clinic. During participant observation of genetics clinic consultations and semi-structured interviews in Urdu or English in respondents’ homes, we identified an array of environmental, behavioral and spiritual understandings of the causes of medical and intellectual problems. Misconceptions about the location of genetic information in the body and of genetic mechanisms of inheritance were common, reflected the range of everyday theories observed for White British patients and included the belief that a child receives more genetic material from the father than the mother. Despite some participants’ conversational use of genetic terminology, some patients had assimilated genetic information in ways that conflict with genetic theory with potentially serious clinical consequences. Additionally, skepticism of genetic theories of illness reflected a rejection of a dominant discourse of genetic risk that stigmatizes cousin marriages. Patients referred to genetics clinics may not easily surrender their lay or personal theories about the causes of their own or their child’s condition and their understandings of genetic risk. Genetic counselors may need to identify, work with and at times challenge patients’ understandings of illness causality and inheritance.

‘I don't see any point in telling them’: attitudes to sharing genetic information in the family and carrier testing of relatives among British Pakistani adults referred to a genetics clinic

The sharing of genetic information following the diagnosis of a genetic condition can be important for managing familial risks for genetic conditions. This paper explores factors that impede or facilitate the sharing of genetic information within a sample of British Pakistani families. It draws from research investigating understandings of genetics and inheritance, attitudes to prenatal diagnosis and risk communication in the family that used methods of participant observation and interview with adults from 66 families of Pakistani origin referred to a genetics clinic in southern England. We found a lack of English often restricted one partners access to genetic information and partners fluent in English sometimes withheld information to protect a partner (usually the wife) from blame, stigma or feelings of marital insecurity. Many couples felt genetic information was private to them as a couple and were unwilling to share it with the wider family, commenting on its potentially stigmatizing and emotionally and socially disruptive effects on themselves, their child and their marriage, as well as on the marriage prospects of other family members. Those who sought carrier testing because of a family history did so when considering their own marriage or parenting, sometimes on the insistence of an affected relative, but did not readily discuss carrier testing with other relatives. Despite the complex consanguinity in some families, a family-based approach to risk management is not necessarily any easier among British Pakistanis than other ethnic groups.

Cataracts, motor system disorder, short stature, learning difficulties, and skeletal abnormalities : A new syndrome ?

We present a 4-generation family in which affected individuals have cataracts, a motor neuronopathy with upper motor neuron signs, short stature, developmental delay, and skeletal abnormalities. An additional symptom is weakness during pregnancy which resolves after delivery. The condition is inherited in an autosomal dominant manner. The manifestations and inheritance are not found in any previously described conditions. We consider that this is a new syndrome.

Potocki-Lupski syndrome mimicking a connective tissue disorder.

Magdalen College, University of Oxford, Oxford NIHR Biomedical Research Centre, The Wellcome Trust Centre for Human Genetics, Department of Clinical Genetics, Churchill Hospital, Headington, Oxford, UK, Department of Genome Sciences, University of Washington School of Medicine and Howard Hughes Medical Institute, Washington, USA Correspondence to U. Kini, Department of Clinical Genetics, Churchill Hospital, Headington, Oxford, UK Tel: + 44 1865 226024; fax: + 44 1865 226011; e-mail: usha.kini@orh.nhs.uk; sujkini@yahoo.co.uk