Paediatrics (RCH) - Research Publications
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ItemNo Preview AvailablePathogenic Variants in GPC4 Cause Keipert Syndrome(CELL PRESS, 2019-05-02)Glypicans are a family of cell-surface heparan sulfate proteoglycans that regulate growth-factor signaling during development and are thought to play a role in the regulation of morphogenesis. Whole-exome sequencing of the Australian family that defined Keipert syndrome (nasodigitoacoustic syndrome) identified a hemizygous truncating variant in the gene encoding glypican 4 (GPC4). This variant, located in the final exon of GPC4, results in premature termination of the protein 51 amino acid residues prior to the stop codon, and in concomitant loss of functionally important N-linked glycosylation (Asn514) and glycosylphosphatidylinositol (GPI) anchor (Ser529) sites. We subsequently identified seven affected males from five additional kindreds with novel and predicted pathogenic variants in GPC4. Segregation analysis and X-inactivation studies in carrier females provided supportive evidence that the GPC4 variants caused the condition. Furthermore, functional studies of recombinant protein suggested that the truncated proteins p.Gln506∗ and p.Glu496∗ were less stable than the wild type. Clinical features of Keipert syndrome included a prominent forehead, a flat midface, hypertelorism, a broad nose, downturned corners of mouth, and digital abnormalities, whereas cognitive impairment and deafness were variable features. Studies of Gpc4 knockout mice showed evidence of the two primary features of Keipert syndrome: craniofacial abnormalities and digital abnormalities. Phylogenetic analysis demonstrated that GPC4 is most closely related to GPC6, which is associated with a bone dysplasia that has a phenotypic overlap with Keipert syndrome. Overall, we have shown that pathogenic variants in GPC4 cause a loss of function that results in Keipert syndrome, making GPC4 the third human glypican to be linked to a genetic syndrome.
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ItemThe novel RAF1 mutation p.(Gly361Ala) located outside the kinase domain of the CR3 region in two patients with Noonan syndrome, including one with a rare brain tumor(WILEY, 2018-02)Noonan syndrome is characterized by typical craniofacial dysmorphism, postnatal growth retardation, congenital heart defect, and learning difficulties and belongs to the RASopathies, a group of neurodevelopmental disorders caused by germline mutations in genes encoding components of the RAS-MAPK pathway. Mutations in the RAF1 gene are associated with Noonan syndrome, with a high prevalence of hypertrophic cardiomyopathy (HCM). RAF1 mutations cluster in exons encoding the conserved region 2 (CR2), the kinase activation segment of the CR3 domain, and the C-terminus. We present two boys with Noonan syndrome and the identical de novo RAF1 missense variant c.1082G>C/p.(Gly361Ala) affecting the CR3, but located outside the kinase activation segment. The p.(Gly361Ala) mutation has been identified as a RAF1 allele conferring resistance to RAF inhibitors. This amino acid change favors a RAF1 conformation that allows for enhanced RAF dimerization and increased intrinsic kinase activity. Both patients with Noonan syndrome showed typical craniofacial dysmorphism, macrocephaly, and short stature. One individual developed HCM and was diagnosed with a disseminated oligodendroglial-like leptomeningeal tumor (DOLT) of childhood at the age of 9 years. While there is a well-established association of NS with malignant tumors, especially childhood hemato-oncological diseases, brain tumors have rarely been reported in Noonan syndrome. Our data demonstrate that mutation scanning of the entire coding region of genes associated with Noonan syndrome is mandatory not to miss rare variants located outside the known mutational hotspots.
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ItemPseudodiastrophic Dysplasia: Two Cases Delineating and Expanding the Pre and Postnatal Phenotype(WILEY-BLACKWELL, 2016-05)
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ItemExploring the speech and language of individuals with non-syndromic submucous cleft palate: a preliminary report(WILEY, 2019-09)BACKGROUND: Submucous cleft palate (SMCP) has a heterogeneous presentation and is often identified late or misdiagnosed. Diagnosis is prompted by speech, resonance or feeding symptoms associated with velopharyngeal insufficiency. However, the broader impacts of SMCP on communication have rarely been examined and therefore are poorly understood. AIM: To describe the communicative profile of individuals with non-syndromic SMCP by examining speech, language and pragmatics (social language). METHODS & PROCEDURES: Fifteen participants with SMCP aged 5;1-12;8, without a genetic diagnosis, participated in the study. Participants completed standardized assessments examining language, resonance, speech and non-verbal intellect. Parents also completed the Children's Communication Checklist (CCC-2), which provided a measure of overall communicative ability, including pragmatic skills. Formal language outcomes were compared with two cohorts: 36 individuals with overt non-syndromic clefts and 129 individuals with no history of clefting. OUTCOMES & RESULTS: Speech intelligibility was reduced secondary to hypernasality, disordered articulation and/or impaired phonology (n = 7) in children with SMCP. Poorer overall language outcomes were observed for children with SMCP compared with both those with overt clefts and no history of clefting (p < 0.001). Language scores for children with SMCP ranged from impaired (n = 6) to above the standardized mean (n = 4). Receptive and expressive language performance were independently correlated with non-verbal IQ (p < 0.01). Those with severe language impairment (n = 4) also had borderline or impaired non-verbal IQ. Parents reported that speech and semantics were the most affected sub-domains of communication, while scores were the highest for the initiation domain. Speech and language skills were correlated strongly with pragmatics (r = 0.877, p < 0.01). CONCLUSIONS & IMPLICATIONS: Overall, performance was variable within the SMCP group across speech, language and pragmatic assessments. In addition to well-documented speech difficulties, children with SMCP may have language or pragmatic impairments, suggesting that further neurodevelopmental influences may be at play. As such, for individuals with SMCP, additional clinical screening of language and pragmatic abilities may be required to ensure accurate diagnosis and guide both cleft and non-cleft related therapy programmes.
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ItemHIST1H1E heterozygous protein-truncating variants cause a recognizable syndrome with intellectual disability and distinctive facial gestalt: A study to clarify the HIST1H1E syndrome phenotype in 30 individuals(WILEY, 2019-10)Histone Gene Cluster 1 Member E, HIST1H1E, encodes Histone H1.4, is one of a family of epigenetic regulator genes, acts as a linker histone protein, and is responsible for higher order chromatin structure. HIST1H1E syndrome (also known as Rahman syndrome, OMIM #617537) is a recently described intellectual disability (ID) syndrome. Since the initial description of five unrelated individuals with three different heterozygous protein-truncating variants (PTVs) in the HIST1H1E gene in 2017, we have recruited 30 patients, all with HIST1H1E PTVs that result in the same shift in frame and that cluster to a 94-base pair region in the HIST1H1E carboxy terminal domain. The identification of 30 patients with HIST1H1E variants has allowed the clarification of the HIST1H1E syndrome phenotype. Major findings include an ID and a recognizable facial appearance. ID was reported in all patients and is most frequently of moderate severity. The facial gestalt consists of a high frontal hairline and full lower cheeks in early childhood and, in later childhood and adulthood, affected individuals have a strikingly high frontal hairline, frontal bossing, and deep-set eyes. Other associated clinical features include hypothyroidism, abnormal dentition, behavioral issues, cryptorchidism, skeletal anomalies, and cardiac anomalies. Brain magnetic resonance imaging (MRI) is frequently abnormal with a slender corpus callosum a frequent finding.
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ItemThe incidence, prevalence and clinical features of MECP2 duplication syndrome in Australian children(WILEY, 2019-11)AIM: The aim of this study was to assess the incidence and prevalence of MECP2 duplication syndrome in Australian children and further define its phenotype. METHODS: The Australian Paediatric Surveillance Unit was used to identify children with MECP2 duplication syndrome between June 2014 and November 2017. Reporting clinicians were invited to complete a questionnaire. Clinician data (n = 20) were supplemented with information from the International Rett Syndrome Phenotype Database and from caregivers (n = 7). Birth prevalence and diagnostic incidence were calculated. RESULTS: The birth prevalence of MECP2 duplication syndrome in Australia was 0.65/100 000 for all live births and 1/100 000 for males. Diagnostic incidence was 0.07/100 000 person-years overall and 0.12/100 000 person-years for males. The median age at diagnosis was 23.5 months (range 0 months-13 years). A history of pneumonia was documented in three quarters of the clinical cases, half of whom had more than nine episodes. Cardiovascular abnormalities were reported in three cases. A clinical vignette is presented for one child who died due to severe idiopathic pulmonary hypertension. The majority (13/15) of males had inherited the duplication from their mothers, and two had an unbalanced translocation. CONCLUSIONS: MECP2 duplication syndrome is a rare but important diagnosis in children because of the burden of respiratory illness and recurrence risk. Pulmonary hypertension is a rare life-threatening complication. Array comparative genomic hybridisation testing is recommended for children with undiagnosed intellectual disability or global developmental delay. Early cardiac assessment and ongoing monitoring is recommended for MECP2 duplication syndrome.
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ItemDiagnostic and service impact of genomic testing technologies in a neonatal intensive care unit(WILEY, 2019-11)AIM: To investigate the diagnostic and service impact of chromosomal microarray and whole exome sequencing (WES) in a neonatal intensive care unit (NICU). METHODS: This was a retrospective medical record review of NICU patients referred for genetics consultation at three time points over a 9-year period at a single centre to determine referral indications, genetic consultation outcomes and time to diagnosis. RESULTS: The number of NICU patients referred for genetics consultation increased from 44 in 2007 to 95 in 2015. The proportion of NICU patients suspected of having a genetic condition following clinical geneticist assessment remained stable, averaging 5.3% of all admissions. The proportion of patients receiving a confirmed diagnosis rose from 21% in 2007 to 53% in 2015, with a shift from primarily chromosomal abnormalities to a broad range of monogenic disorders, increasingly diagnosed by WES as a first-tier test. The average age at diagnosis in 2015 was 19 days (range 12-38 days) for chromosomal abnormalities and 138 days (range 10-309 days) for monogenic conditions. CONCLUSIONS: The adoption of new genetic technologies at our centre has increased the proportion of patients receiving a confirmed genetic diagnosis. This study provides important benchmark data to measure further improvements as turn-around times for genomic testing decrease.
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ItemCerebral palsy and genomics: an international consortium(WILEY, 2018-02)