A Meier-Gorlin syndrome mutation impairs the ORC1-nucleosome association.
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ABSTRACT:
SUBMITTER: Zhang W
PROVIDER: S-EPMC4654454 | biostudies-literature | 2015 May
REPOSITORIES: biostudies-literature
Publications
A Meier-Gorlin syndrome mutation impairs the ORC1-nucleosome association.
Zhang Wei W Sankaran Saumya S Gozani Or O Song Jikui J
ACS chemical biology 20150224 5
Recent studies have identified several genetic mutations within the BAH domain of human Origin Recognition Complex subunit 1 (hORC1BAH), including the R105Q mutation, implicated in Meier-Gorlin Syndrome (MGS). However, the pathological role of the hORC1 R105Q mutation remains unclear. In this study, we have investigated the interactions of the hORC1BAH domain with histone H4K20me2, DNA, and the nucleosome core particle labeled with H4Kc20me2, a chemical analog of H4K20me2. Our study revealed a n ...[more]
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Project description:Meier-Gorlin syndrome (MGS) is a rare autosomal recessive primordial dwarfism disorder, characterized by microtia, patellar applasia/hypoplasia, and a proportionate short stature. Associated clinical features encompass feeding problems, congenital pulmonary emphysema, mammary hypoplasia in females and urogenital anomalies, such as cryptorchidism and hypoplastic labia minora and majora. Typical facial characteristics during childhood comprise a small mouth with full lips and micro-retrognathia. During ageing, a narrow, convex nose becomes more prominent. The diagnosis MGS should be considered in patients with at least two of the three features of the clinical triad of microtia, patellar anomalies, and pre- and postnatal growth retardation. In patients with short stature and/or microtia, the patellae should be assessed with care by ultrasonography before age 6 or radiography thereafter. Mutations in one of five genes (ORC1, ORC4, ORC6, CDT1, and CDC6) of the pre-replication complex, involved in DNA-replication, are detected in approximately 67-78% of patients with MGS. Patients with ORC1 and ORC4 mutations appear to have the most severe short stature and microcephaly. Management should be directed towards in-depth investigation, treatment and prevention of associated problems, such as growth retardation, feeding problems, hearing loss, luxating patellae, knee pain, gonarthrosis, and possible pulmonary complications due to congenital pulmonary emphysema with or without broncho- or laryngomalacia. Growth hormone treatment is ineffective in most patients with MGS, but may be effective in patients in whom growth continues to decrease after the first year of life (usually growth velocity normalizes after the first year) and with low levels of IGF1. At present, few data is available about reproduction of females with MGS, but the risk of premature labor might be increased. Here, we propose experience-based guidelines for the regular care and treatment of MGS patients.
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Project description:The recognition of distinctly modified histones by specialized 'effector' proteins constitutes a key mechanism for transducing molecular events at chromatin to biological outcomes. Effector proteins influence DNA-templated processes, including transcription, DNA recombination and DNA repair; however, no effector functions have yet been identified within the mammalian machinery that regulate DNA replication. Here we show that ORC1--a component of ORC (origin of replication complex), which mediates pre-DNA replication licensing--contains a bromo adjacent homology (BAH) domain that specifically recognizes histone H4 dimethylated at lysine 20 (H4K20me2). Recognition of H4K20me2 is a property common to BAH domains present within diverse metazoan ORC1 proteins. Structural studies reveal that the specificity of the BAH domain for H4K20me2 is mediated by a dynamic aromatic dimethyl-lysine-binding cage and multiple intermolecular contacts involving the bound peptide. H4K20me2 is enriched at replication origins, and abrogating ORC1 recognition of H4K20me2 in cells impairs ORC1 occupancy at replication origins, ORC chromatin loading and cell-cycle progression. Mutation of the ORC1 BAH domain has been implicated in the aetiology of Meier-Gorlin syndrome (MGS), a form of primordial dwarfism, and ORC1 depletion in zebrafish results in an MGS-like phenotype. We find that wild-type human ORC1, but not ORC1-H4K20me2-binding mutants, rescues the growth retardation of orc1 morphants. Moreover, zebrafish depleted of H4K20me2 have diminished body size, mirroring the phenotype of orc1 morphants. Together, our results identify the BAH domain as a novel methyl-lysine-binding module, thereby establishing the first direct link between histone methylation and the metazoan DNA replication machinery, and defining a pivotal aetiological role for the canonical H4K20me2 mark, via ORC1, in primordial dwarfism.
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Project description:Meier-Gorlin syndrome (ear, patella and short-stature syndrome) is an autosomal recessive primordial dwarfism syndrome characterized by absent or hypoplastic patellae and markedly small ears¹?³. Both pre- and post-natal growth are impaired in this disorder, and although microcephaly is often evident, intellect is usually normal in this syndrome. We report here that individuals with this disorder show marked locus heterogeneity, and we identify mutations in five separate genes: ORC1, ORC4, ORC6, CDT1 and CDC6. All of these genes encode components of the pre-replication complex, implicating defects in replication licensing as the cause of a genetic syndrome with distinct developmental abnormalities.
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Project description:BackgroundMeier-Gorlin syndrome 7 (MGS7) is a rare autosomal recessive condition. We reported a fetus diagnosed with Meier-Gorlin syndrome 7. The antenatal sonographic images were presented, and compound heterozygous mutations of CDC45 on chromosome 22 were identified by whole-exome sequencing (WES).Case presentationFetal growth restriction (FGR), craniosynostosis, and brachydactyly of right thumb were found in a fetus of 28th gestational weeks. The fetus was diagnosed as MGS7 clinically. After extensive counseling, the couple opted for prenatal diagnosis by cordocentesis and termination of pregnancy. Karyotype analysis and WES were performed. Chromosomal karyotyping showed that the fetus was 46, XY. There were 2 mutations of CDC45, the causal gene of MGS7 on chromosome 22, which were inherited from the couple respectively were identified by WES. Facial dysmorphism, brachydactyly of right thumb, and genitalia abnormally were proved by postpartum autopsy, and craniosynostosis was confirmed by three-dimensional computed tomography (3D-CT) reconstruction.ConclusionsIt is possible to detect multiple clinical features of Meier-Gorlin syndrome in prenatal sonography. Deteriorative FGR complicated with craniosynostosis indicates MGS7. Combination of 2D and 3D ultrasonography helps to detect craniosynostosis. The affected fetus was confirmed a compound heterozygote of CDC45 related MGS by whole-exome sequencing, which is critical in identifying rare genetic diseases.
| S-EPMC8130261 | biostudies-literature
Project description:Meier-Gorlin syndrome is a rare recessive disorder characterized by a number of distinct tissue-specific developmental defects. Genes encoding members of the origin recognition complex (ORC) and additional proteins essential for DNA replication (CDC6, CDT1, GMNN, CDC45, MCM5, and DONSON) are mutated in individuals diagnosed with MGS. The essential role of ORC is to license origins during the G1 phase of the cell cycle, but ORC has also been implicated in several nonreplicative functions. Because of its essential role in DNA replication, ORC is required for every cell division during development. Thus, it is unclear how the Meier-Gorlin syndrome mutations in genes encoding ORC lead to the tissue-specific defects associated with the disease. To begin to address these issues, we used Cas9-mediated genome engineering to generate a Drosophila melanogaster model of individuals carrying a specific Meier-Gorlin syndrome mutation in ORC4 along with control strains. Together these strains provide the first metazoan model for an MGS mutation in which the mutation was engineered at the endogenous locus along with precisely defined control strains. Flies homozygous for the engineered MGS allele reach adulthood, but with several tissue-specific defects. Genetic analysis revealed that this Orc4 allele was a hypomorph. Mutant females were sterile, and phenotypic analyses suggested that defects in DNA replication was an underlying cause. By leveraging the well-studied Drosophila system, we provide evidence that a disease-causing mutation in Orc4 disrupts DNA replication, and we propose that in individuals with MGS defects arise preferentially in tissues with a high-replication demand.
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Project description:In eukaryotes, DNA replication requires the origin recognition complex (ORC), a six-subunit assembly that promotes replisome formation on chromosomal origins. Despite extant homology between certain subunits, the degree of structural and organizational overlap between budding yeast and metazoan ORC has been unclear. Using 3D electron microscopy, we determined the subunit organization of metazoan ORC, revealing that it adopts a global architecture very similar to the budding yeast complex. Bioinformatic analysis extends this conservation to Orc6, a subunit of somewhat enigmatic function. Unexpectedly, a mutation in the Orc6 C-terminus linked to Meier-Gorlin syndrome, a dwarfism disorder, impedes proper recruitment of Orc6 into ORC; biochemical studies reveal that this region of Orc6 associates with a previously uncharacterized domain of Orc3 and is required for ORC function and MCM2-7 loading in vivo. Together, our results suggest that Meier-Gorlin syndrome mutations in Orc6 impair the formation of ORC hexamers, interfering with appropriate ORC functions. DOI:http://dx.doi.org/10.7554/eLife.00882.001.
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Project description:IntroductionReplication of the nuclear genome is an essential step for cell division. Pathogenic variants in genes coding for highly conserved components of the DNA replication machinery cause Meier-Gorlin syndrome (MGORS).ObjectiveIdentification of novel genes associated with MGORS.MethodsExome sequencing was performed to investigate the genotype of an individual presenting with prenatal and postnatal growth restriction, a craniofacial gestalt of MGORS and coronal craniosynostosis. The analysis of the candidate variants employed bioinformatic tools, in silico structural protein analysis and modelling in budding yeast.ResultsA novel homozygous missense variant NM_016095.2:c.341G>T, p.(Arg114Leu), in GINS2 was identified. Both non-consanguineous healthy parents carried this variant. Bioinformatic analysis supports its classification as pathogenic. Functional analyses using yeast showed that this variant increases sensitivity to nicotinamide, a compound that interferes with DNA replication processes. The phylogenetically highly conserved residue p.Arg114 localises at the docking site of CDC45 and MCM5 at GINS2. Moreover, the missense change possibly disrupts the effective interaction between the GINS complex and CDC45, which is necessary for the CMG helicase complex (Cdc45/MCM2-7/GINS) to accurately operate. Interestingly, our patient's phenotype is strikingly similar to the phenotype of patients with CDC45-related MGORS, particularly those with craniosynostosis, mild short stature and patellar hypoplasia.ConclusionGINS2 is a new disease-associated gene, expanding the genetic aetiology of MGORS.
| S-EPMC9340002 | biostudies-literature
Project description:Meier-Gorlin syndrome (MGS) is a genetically heterogeneous primordial dwarfism syndrome known to be caused by biallelic loss-of-function mutations in one of five genes encoding pre-replication complex proteins: ORC1, ORC4, ORC6, CDT1, and CDC6. Mutations in these genes cause disruption of the origin of DNA replication initiation. To date, only an autosomal-recessive inheritance pattern has been described in individuals with this disorder, with a molecular etiology established in about three-fourths of cases. Here, we report three subjects with MGS and de novo heterozygous mutations in the 5' end of GMNN, encoding the DNA replication inhibitor geminin. We identified two truncating mutations in exon 2 (the 1(st) coding exon), c.16A>T (p.Lys6(?)) and c.35_38delTCAA (p.Ile12Lysfs(?)4), and one missense mutation, c.50A>G (p.Lys17Arg), affecting the second-to-last nucleotide of exon 2 and possibly RNA splicing. Geminin is present during the S, G2, and M phases of the cell cycle and is degraded during the metaphase-anaphase transition by the anaphase-promoting complex (APC), which recognizes the destruction box sequence near the 5' end of the geminin protein. All three GMNN mutations identified alter sites 5' to residue Met28 of the protein, which is located within the destruction box. We present data supporting a gain-of-function mechanism, in which the GMNN mutations result in proteins lacking the destruction box and hence increased protein stability and prolonged inhibition of replication leading to autosomal-dominant MGS.
| S-EPMC4678788 | biostudies-literature