Publications by authors named "Nerine Gregersen"

14 Publications

  • Page 1 of 1

Phosphodiesterase 3A and Arterial Hypertension.

Circulation 2020 Jul 11;142(2):133-149. Epub 2020 Jun 11.

Leibniz-Forschingsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany (J.E., M.L., B.W.).

Background: High blood pressure is the primary risk factor for cardiovascular death worldwide. Autosomal dominant hypertension with brachydactyly clinically resembles salt-resistant essential hypertension and causes death by stroke before 50 years of age. We recently implicated the gene encoding phosphodiesterase 3A (); however, in vivo modeling of the genetic defect and thus showing an involvement of mutant PDE3A is lacking.

Methods: We used genetic mapping, sequencing, transgenic technology, CRISPR-Cas9 gene editing, immunoblotting, and fluorescence resonance energy transfer. We identified new patients, performed extensive animal phenotyping, and explored new signaling pathways.

Results: We describe a novel mutation within a 15 base pair (bp) region of the gene and define this segment as a mutational hotspot in hypertension with brachydactyly. The mutations cause an increase in enzyme activity. A CRISPR/Cas9-generated rat model, with a 9-bp deletion within the hotspot analogous to a human deletion, recapitulates hypertension with brachydactyly. In mice, mutant transgenic PDE3A overexpression in smooth muscle cells confirmed that mutant PDE3A causes hypertension. The mutant PDE3A enzymes display consistent changes in their phosphorylation and an increased interaction with the 14-3-3θ adaptor protein. This aberrant signaling is associated with an increase in vascular smooth muscle cell proliferation and changes in vessel morphology and function.

Conclusions: The mutated gene drives mechanisms that increase peripheral vascular resistance causing hypertension. We present 2 new animal models that will serve to elucidate the underlying mechanisms further. Our findings could facilitate the search for new antihypertensive treatments.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.119.043061DOI Listing
July 2020

Genetic abnormalities in a large cohort of Coffin-Siris syndrome patients.

J Hum Genet 2019 Dec 17;64(12):1173-1186. Epub 2019 Sep 17.

Asahikawa-Kosei General Hospital, Hokkaido, Japan.

Coffin-Siris syndrome (CSS, MIM#135900) is a congenital disorder characterized by coarse facial features, intellectual disability, and hypoplasia of the fifth digit and nails. Pathogenic variants for CSS have been found in genes encoding proteins in the BAF (BRG1-associated factor) chromatin-remodeling complex. To date, more than 150 CSS patients with pathogenic variants in nine BAF-related genes have been reported. We previously reported 71 patients of whom 39 had pathogenic variants. Since then, we have recruited an additional 182 CSS-suspected patients. We performed comprehensive genetic analysis on these 182 patients and on the previously unresolved 32 patients, targeting pathogenic single nucleotide variants, short insertions/deletions and copy number variations (CNVs). We confirmed 78 pathogenic variations in 78 patients. Pathogenic variations in ARID1B, SMARCB1, SMARCA4, ARID1A, SOX11, SMARCE1, and PHF6 were identified in 48, 8, 7, 6, 4, 1, and 1 patients, respectively. In addition, we found three CNVs including SMARCA2. Of particular note, we found a partial deletion of SMARCB1 in one CSS patient and we thoroughly investigated the resulting abnormal transcripts.
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http://dx.doi.org/10.1038/s10038-019-0667-4DOI Listing
December 2019

Saccular Cyst and Airway Compromise in a New Born With Ciliopathy.

Ear Nose Throat J 2020 May 8;99(4):NP40-NP41. Epub 2019 Apr 8.

Paediatric Otolaryngology, Starship Children's Hospital, Auckland, New Zealand.

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http://dx.doi.org/10.1177/0145561319840206DOI Listing
May 2020

The genetics of recurrent hydatidiform moles: new insights and lessons from a comprehensive analysis of 113 patients.

Mod Pathol 2018 07 20;31(7):1116-1130. Epub 2018 Feb 20.

Département de Génétique Médicale, Hôpital Arnaud de Villeneuve, 371 avenue du Doyen Gaston Giraud, 34295, Montpellier cedex 5, France.

Hydatidiform mole is an aberrant human pregnancy characterized by early embryonic arrest and excessive trophoblastic proliferation. Recurrent hydatidiform moles are defined by the occurrence of at least two hydatidiform moles in the same patient. Fifty to eighty percent of patients with recurrent hydatidiform moles have biallelic pathogenic variants in NLRP7 or KHDC3L. However, in the remaining patients, the genotypic types of the moles are unknown. We characterized 80 new hydatidiform mole tissues, 57 of which were from patients with no mutations in the known genes, and we reviewed the genotypes of a total of 123 molar tissues. We also reviewed mutation analysis in 113 patients with recurrent hydatidiform moles. While all hydatidiform moles from patients with biallelic NLRP7 or KHDC3L mutations are diploid biparental, we demonstrate that those from patients without mutations are highly heterogeneous and only a small minority of them are diploid biparental (8%). The other mechanisms that were found to recur in patients without mutations are diploid androgenetic monospermic (24%) and triploid dispermic (32%); the remaining hydatidiform moles were misdiagnosed as moles due to errors in the analyses and/or their unusual mechanisms. We compared three parameters of genetic susceptibility in patients with and without mutations and show that patients without mutations are mostly from non-familial cases, have fewer reproductive losses, and more live births. Our data demonstrate that patients with recurrent hydatidiform moles and no mutations in the known genes are, in general, different from those with mutations; they have a milder genetic susceptibility and/or a multifactorial etiology underlying their recurrent hydatidiform moles. Categorizing these patients according to the genotypic types of their recurrent hydatidiform moles may facilitate the identification of novel genes for this entity.
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http://dx.doi.org/10.1038/s41379-018-0031-9DOI Listing
July 2018

A craniosynostosis massively parallel sequencing panel study in 309 Australian and New Zealand patients: findings and recommendations.

Genet Med 2018 09 7;20(9):1061-1068. Epub 2017 Dec 7.

Genetic Health Service New Zealand, Christchurch Hospital, Christchurch, New Zealand.

Purpose: The craniosynostoses are characterized by premature fusion of one or more cranial sutures. The relative contribution of previously reported genes to craniosynostosis in large cohorts is unclear. Here we report on the use of a massively parallel sequencing panel in individuals with craniosynostosis without a prior molecular diagnosis.

Methods: A 20-gene panel was designed based on the genes' association with craniosynostosis, and clinically validated through retrospective testing of an Australian and New Zealand cohort of 233 individuals with craniosynostosis in whom previous testing had not identified a causative variant within FGFR1-3 hot-spot regions or the TWIST1 gene. An additional 76 individuals were tested prospectively.

Results: Pathogenic or likely pathogenic variants in non-FGFR genes were identified in 43 individuals, with diagnostic yields of 14% and 15% in retrospective and prospective cohorts, respectively. Variants were identified most frequently in TCF12 (N = 22) and EFNB1 (N = 8), typically in individuals with nonsyndromic coronal craniosynostosis or TWIST1-negative clinically suspected Saethre-Chotzen syndrome. Clinically significant variants were also identified in ALX4, EFNA4, ERF, and FGF10.

Conclusion: These findings support the clinical utility of a massively parallel sequencing panel for craniosynostosis. TCF12 and EFNB1 should be included in genetic testing for nonsyndromic coronal craniosynostosis or clinically suspected Saethre-Chotzen syndrome.
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http://dx.doi.org/10.1038/gim.2017.214DOI Listing
September 2018

12q14 Microdeletions: Additional Case Series with Confirmation of a Macrocephaly Region.

Case Rep Genet 2015 22;2015:192071. Epub 2015 Jul 22.

Diagnostic Genetics, LabPLUS, Auckland City Hospital, P.O. Box 110031, Auckland 1148, New Zealand.

To date, there have been only a few reports of patients carrying a microdeletion in chromosome 12q14. These patients usually present with pre- and postnatal growth retardation, and developmental delay. Here we report on two additional patients with both genotype and phenotype differences. Similar to previously published cases, one patient has haploinsufficiency of the HMGA2 gene and shows severe short stature and developmental delay. The second patient is only one of a handful without the loss of the HMGA2 gene and shows a much better growth profile, but with absolute macrocephaly. This patient's deletion is unique and hence defines a likely macrocephaly locus that contributes to the general phenotype characterising the 12q14 syndrome.
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http://dx.doi.org/10.1155/2015/192071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4525753PMC
August 2015

Thyroid dysfunction in a cohort of South African children with Down syndrome.

S Afr Med J 2013 Jul 29;103(12 Suppl 1):966-70. Epub 2013 Jul 29.

Division of Human Genetics, National Health Laboratory Service and School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.

Background: While international studies show thyroid dysfunction occurs more commonly in individuals with Down syndrome (DS) than in the general population, there is a paucity of available data from sub-Saharan Africa.

Objectives: To document the range of thyroid function in a cohort of South African children with DS, and to assess referral and treatment practices when thyroid dysfunction was present.

Methods: A retrospective file-based study of 391 children with DS seen at the genetic clinics at three Johannesburg hospitals from 2003 to 2008. Thyroid function test (TFT) results (thyroid-stimulating hormone and free thyroxine) and demographic details were collected for each child. Endocrine clinic files from two of the hospitals were reviewed for additional referral and treatment information.

Results: The majority (83.6%) of children had at least one TFT, in most cases performed between the ages of 2 and 12 months. The most common form of thyroid dysfunction was subclinical hypothyroidism (SCH) (28.7%). Up to one-third of the patients, including several neonates with abnormal results, were not referred for further evaluation and were therefore not receiving the necessary treatment. Inter- laboratory biochemical discrepancies and lack of population-specific reference ranges complicated the interpretation of results. The controversy surrounding whether, and how, to treat SCH influenced treatment practices.

Conclusions: Thyroid dysfunction is prevalent in South African children with DS. There is an urgent need to address the laboratory biochemical discrepancies, and to establish guidelines for surveillance and treatment to prevent further irreversible neurological and physical impairment.
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http://dx.doi.org/10.7196/samj.7111DOI Listing
July 2013

Clinical Outcomes and Counselling Issues regarding Partial Trisomy of Terminal Xp in a Child with Developmental Delay.

Sultan Qaboos Univ Med J 2013 May 9;13(2):311-7. Epub 2013 May 9.

Diagnostic Genetics, LabPLUS, Auckland, New Zealand;

Female carriers of balanced translocations involving an X chromosome and an autosome offer genetic counselling challenges. This is in view of the number of possible meiotic outcomes, but also due to the impact of X chromosome-localised genes that are no longer subject to gene silencing through the X chromosome inactivation centre. We present a case where delineation of the extent of X chromosome-localised genes on the derivative autosome using molecular karyotyping offers critical information in the context of genetic counselling.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3706124PMC
http://dx.doi.org/10.12816/0003240DOI Listing
May 2013

The Greater Sekhukhune-CAPABILITY outreach project.

J Community Genet 2013 Jul 11;4(3):335-41. Epub 2013 Jul 11.

Division of Human Genetics, National Health Laboratory Service and University of the Witwatersrand, PO Box 1038, Johannesburg, South Africa.

The Greater Sekhukhune-CAPABILITY Outreach Project was undertaken in a rural district in Limpopo, South Africa, as part of the European Union-funded CAPABILITY programme to investigate approaches for capacity building for the translation of genetic knowledge into care and prevention of congenital disorders. Based on previous experience of a clinical genetic outreach programme in Limpopo, it aimed to initiate a district clinical genetic service in Greater Sekhukhune to gain knowledge and experience to assist in the implementation and development of medical genetic services in South Africa. Implementing the service in Greater Sekhukhune was impeded by a developing staff shortage in the province and pressure on the health service from the existing HIV/AIDS and TB epidemics. This situation underscores the need for health needs assessment for developing services for the care and prevention of congenital disorders in middle- and low-income countries. However, these impediments stimulated the pioneering of innovate ways to offer medical genetic services in these circumstances, including tele-teaching of nurses and doctors, using cellular phones to enhance clinical care and adapting and assessing the clinical utility of a laboratory test, QF-PCR, for use in the local circumstances.
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http://dx.doi.org/10.1007/s12687-013-0149-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3739856PMC
July 2013

Delineation of 2q32q35 deletion phenotypes: two apparent "proximal" and "distal" syndromes.

Case Rep Genet 2013 9;2013:823451. Epub 2013 Jun 9.

Diagnostic Genetics, LabPlus, Auckland City Hospital, P.O. Box 110031, Auckland 1148, New Zealand.

We report on three patients with interstitial deletions of the long arm of chromosome 2 involving bands 2q32.1-q35. They presented with wide-ranging phenotypic variation including facial dysmorphisms, cleft palate, learning difficulties, behavioural issues and severe heart defects. Microarray analysis confirmed an 8.6 Mb deletion in patients 1 and 2 and a 24.7 Mb deletion in patient 3. We discuss the genes involved in the deleted regions including MYO1B, GLS, FRZB, SATB2, and CPS1 and compare the phenotype with those reported in the literature. Taken together, these data suggest that there is a spectrum of disease severity such that patients with deletions encompassing the region of 2q32.1q32.2, which includes the FRZB gene, show an apparently milder phenotype compared to those that lie further distal in 2q32.3q35 that encompasses the SATB2 gene.
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http://dx.doi.org/10.1155/2013/823451DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3690635PMC
July 2013

Developmental delay referrals and the roles of Fragile X testing and molecular karyotyping: a New Zealand perspective.

Mol Med Rep 2013 May 20;7(5):1710-4. Epub 2013 Mar 20.

Diagnostic Genetics, LabPlus, Auckland City Hospital, and School of Biological Sciences, University of Auckland, Auckland 1148, New Zealand.

Global developmental delay (GDD) affects ~1-3% of children, many of whom will also have intellectual disability (ID). Fragile X is the major genetic cause of GDD with mental retardation (MR) in males, accounting for ~20% of all X-linked MR. As Fragile X has serious genetic implications, the overwhelming majority of developmental delay (DD) cases referred to our laboratory are concerned with the exclusion of a diagnosis of Fragile X, along with simultaneous karyotype analysis to confirm chromosome aberrations. Critically, molecular laboratories have generally experienced a falling positive detection frequency of Fragile X. In this context, the recent implementation of array‑based techno-logy has significantly increased the likelihood of detecting chromosome aberrations that underpin DD. In the current study, we report a Fragile X mutation detection frequency for DD referrals that is comparable with the falling UK detection frequencies. In addition, we find that there is a 9‑fold greater likelihood of detecting clinically significant chromosomal aberrations than of detecting a full Fragile X mental retardation 1 (FMR1) gene CGG repeat expansion in cases referred on the basis of DD. We propose a more efficent sequential testing algorithm that involves an initial molecular karyotype, cascading to FMR1 gene analysis in the event of a negative result.
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http://dx.doi.org/10.3892/mmr.2013.1386DOI Listing
May 2013

Novel CYP2C9 and VKORC1 gene variants associated with warfarin dosage variability in the South African black population.

Pharmacogenomics 2011 Jul 2;12(7):953-63. Epub 2011 Jun 2.

Division of Human Genetics, The National Health Laboratory Service & School of Pathology, The University of Witwatersrand, Johannesburg, South Africa.

Aim: Warfarin is a widely used therapeutic agent for long-term oral anticoagulation worldwide. Its administration is challenging owing to its narrow therapeutic range and serious adverse effects. Several environmental factors and numerous genes, of which CYP2C9 and VKORC1 are the most important, have been associated with interindividual dosage variability. Many studies have been conducted to understand warfarin dosage variability better, the majority of which have been focused on the Caucasian and African-American populations. Very little information is available regarding genetic influences of warfarin dosage variability in the South African black population.

Materials & Methods: In this study, we genotyped 213 South African black individuals for CYP2C9 and VKORC1 variants and a small subset of environmental factors that may be responsible for warfarin dosage variability.

Results: We observed 26 novel SNPs and seven previously described CYP2C9 variants and three previously described but no novel VKORC1 SNPs. Only 11 of the CYP2C9 variants and two of the VKORC1 variants were observed at high enough allele frequencies to assess their impact on warfarin dosage.

Conclusion: We demonstrate that CYP2C9*8 and two novel CYP2C9 SNPs (g.16179 and g.46028) are associated with a decrease in warfarin dosage, β-blockers are independently associated with a decrease in warfarin dosage and two known VKORC1 variants (rs7200749 and rs7294) are associated with an increase in warfarin dosage. The CYP2C9 and VKORC1 variants and a small subset of environmental factors used in the study explain approximately 45% of warfarin dosage variability in the South African black population.
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http://dx.doi.org/10.2217/pgs.11.36DOI Listing
July 2011

Facial asymmetry with colon atresia.

Authors:
Nerine Gregersen

Clin Dysmorphol 2006 Jan;15(1):45-6

National Health Laboratory Services and University of the Witwatersrand, Johannesburg, South Africa.

This case report describes an unusual combination of birth defects in a black South African child presenting with colon atresia, facial symmetry due to facial microsomia and brain abnormalities. The suspected aetiology is thought to be vascular disruption in the late embryonic period.
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http://dx.doi.org/10.1097/01.mcd.0000175604.03221.adDOI Listing
January 2006

Costello syndrome with growth hormone deficiency and hypoglycemia: a new report and review of the endocrine associations.

Am J Med Genet A 2004 Aug;129A(2):171-5

Division of Human Genetics, School of Pathology, National Health Laboratory Services, University of the Witwatersrand, Johannesburg, South Africa.

We describe an 18-month-old boy with Costello syndrome (CS) with proven partial growth hormone (GH) deficiency and hypoglycemic episodes. The hypoglycemia is deemed to be due to cortisol deficiency. This report represents the second published case of cortisol deficiency in the CS. A brief review of the endocrine disturbances in the syndrome is provided. We highlight the need for careful endocrinological evaluation of individuals with CS.
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http://dx.doi.org/10.1002/ajmg.a.30189DOI Listing
August 2004