title: Very small deletions within the NESP55 gene in pseudohypoparathyroidism type 1b.
abstract: Pseudohypoparathyroidism (PHP) is caused by reduced expression of genes within the GNAS cluster, resulting in parathormone resistance. The cluster contains multiple imprinted transcripts, including the stimulatory G protein α subunit (Gs-α) and NESP55 transcript preferentially expressed from the maternal allele, and the paternally expressed XLas, A/B and antisense transcripts. PHP1b can be caused by loss of imprinting affecting GNAS A/B alone (associated with STX16 deletion), or the entire GNAS cluster (associated with deletions of NESP55 in a minority of cases). We performed targeted genomic next-generation sequencing (NGS) of the GNAS cluster to seek variants and indels underlying PHP1b. Seven patients were sequenced by hybridisation-based capture and fourteen more by long-range PCR and transposon-mediated insertion and sequencing. A bioinformatic pipeline was developed for variant and indel detection. In one family with two affected siblings, and in a second family with a single affected individual, we detected maternally inherited deletions of 40 and 33 bp, respectively, within the deletion previously reported in rare families with PHP1b. All three affected individuals presented with atypically severe PHP1b; interestingly, the unaffected mother in one family had the detected deletion on her maternally inherited allele. Targeted NGS can reveal sequence changes undetectable by current diagnostic methods. Identification of genetic mutations underlying epigenetic changes can facilitate accurate diagnosis and counselling, and potentially highlight genetic elements critical for normal imprint setting.
authors.affiliation: Human Genetics and Genomic medicine, Faculty of Medicine, University of Southampton, Southampton, UK.
authors.forename: Faisal I
authors.initials: FI
authors.lastname: Rezwan
authors.affiliation: 1] Human Genetics and Genomic medicine, Faculty of Medicine, University of Southampton, Southampton, UK [2] Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury NHS Foundation Trust, Salisbury, UK.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Poole
authors.affiliation: Department of Medical Genetics, Oslo University Hospital, Oslo, Norway.
authors.forename: Trine
authors.initials: T
authors.lastname: Prescott
authors.affiliation: Queen Alexandra Hospital, Portsmouth, UK.
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Walker
authors.affiliation: 1] Human Genetics and Genomic medicine, Faculty of Medicine, University of Southampton, Southampton, UK [2] Wessex Clinical Genetics Service, Princess Anne Hospital, University Hospital Southampton NHS Foundation Trust, Southampton, UK.
authors.forename: I
authors.initials: I
authors.lastname: Karen Temple
authors.affiliation: 1] Human Genetics and Genomic medicine, Faculty of Medicine, University of Southampton, Southampton, UK [2] Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury NHS Foundation Trust, Salisbury, UK.
authors.forename: Deborah J G
authors.initials: DJ
authors.lastname: Mackay
mesh_terms: D000293:Adolescent; D000483:Alleles; D002675:Child, Preschool; D002864:Chromogranins; D019295:Computational Biology; D019175:DNA Methylation; D005260:Female; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics*; D017353:Gene Deletion; D056426:Genetic Loci; D014644:Genetic Variation; D018392:Genomic Imprinting; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D008297:Male; D005810:Multigene Family; D010375:Pedigree; D011547:Pseudohypoparathyroidism / Q000175:diagnosis* / Q000235:genetics*; D017422:Sequence Analysis, DNA; D051438:Syntaxin 16 / Q000235:genetics; D055815:Young Adult
chemical_list: D002864:Chromogranins; C496118:STX16 protein, human; D051438:Syntaxin 16; C406732:GNAS protein, human; D019205:GTP-Binding Protein alpha Subunits, Gs