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1.
Eur J Hum Genet ; 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31534215

RESUMO

Ciliopathy disorders due to abnormalities of motile cilia encompass a range of autosomal recessive conditions typified by chronic otosinopulmonary disease, infertility, situs abnormalities and hydrocephalus. Using a combination of genome-wide SNP mapping and whole exome sequencing (WES), we investigated the genetic cause of a form of situs inversus (SI) and male infertility present in multiple individuals in an extended Amish family, assuming that an autosomal recessive founder variant was responsible. This identified a single shared (2.34 Mb) region of autozygosity on chromosome 15q21.3 as the likely disease locus, in which we identified a single candidate biallelic frameshift variant in MNS1 [NM_018365.2: c.407_410del; p.(Glu136Glyfs*16)]. Genotyping of multiple family members identified randomisation of the laterality defects in other homozygous individuals, with all wild type or MNS1 c.407_410del heterozygous carriers being unaffected, consistent with an autosomal recessive mode of inheritance. This study identifies an MNS1 variant as a cause of laterality defects and male infertility in humans, mirroring findings in Mns1-deficient mice which also display male infertility and randomisation of left-right asymmetry of internal organs, confirming a crucial role for MNS1 in nodal cilia and sperm flagella formation and function.

2.
Sci Rep ; 9(1): 13229, 2019 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-31519934

RESUMO

Nystagmus is a disorder of uncontrolled eye movement and can occur as an isolated trait (idiopathic INS, IINS) or as part of multisystem disorders such as albinism, significant visual disorders or neurological disease. Eighty-one unrelated patients with nystagmus underwent routine ocular phenotyping using commonly available phenotyping methods and were grouped into four sub-cohorts according to the level of phenotyping information gained and their findings. DNA was extracted and sequenced using a broad utility next generation sequencing (NGS) gene panel. A clinical subpanel of genes for nystagmus/albinism was utilised and likely causal variants were prioritised according to methods currently employed by clinical diagnostic laboratories. We determine the likely underlying genetic cause for 43.2% of participants with similar yields regardless of prior phenotyping. This study demonstrates that a diagnostic workflow combining basic ocular phenotyping and a clinically available targeted NGS panel, can provide a high diagnostic yield for patients with infantile nystagmus, enabling access to disease specific management at a young age and reducing the need for multiple costly, often invasive tests. By describing diagnostic yield for groups of patients with incomplete phenotyping data, it also permits the subsequent design of 'real-world' diagnostic workflows and illustrates the changing role of genetic testing in modern diagnostic workflows for heterogeneous ophthalmic disorders.

3.
Lancet Neurol ; 18(12): 1136-1146, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31377012

RESUMO

Hereditary spastic paraplegia (HSP) describes a heterogeneous group of genetic neurodegenerative diseases characterised by progressive spasticity of the lower limbs. The pathogenic mechanism, associated clinical features, and imaging abnormalities vary substantially according to the affected gene and differentiating HSP from other genetic diseases associated with spasticity can be challenging. Next generation sequencing-based gene panels are now widely available but have limitations and a molecular diagnosis is not made in most suspected cases. Symptomatic management continues to evolve but with a greater understanding of the pathophysiological basis of individual HSP subtypes there are emerging opportunities to provide targeted molecular therapies and personalised medicine.

4.
BMC Med Genet ; 20(1): 145, 2019 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-31443639

RESUMO

BACKGROUND: Inherited palmoplantar keratodermas (PPKs) are clinically and genetically heterogeneous and phenotypically diverse group of genodermatoses characterized by hyperkeratosis of the palms and soles. More than 20 genes have been reported to be associated with PPKs including desmoglein 1 (DSG1) a key molecular component for epidermal adhesion and differentiation. Mal de Meleda (MDM) is a rare inherited autosomal recessive genodermatosis characterized by transgrediens PPK, associated with mutations in the secreted LY6/PLAUR domain containing 1 (SLURP1) gene. METHODS: This study describes clinical as well as genetic whole exome sequencing (WES) and di-deoxy sequencing investigations in two Pakistani families with a total of 12 individuals affected by PPK. RESULTS: WES identified a novel homozygous nonsense variant in SLURP1, and a novel heterozygous nonsense variant in DSG1, as likely causes of the conditions in each family. CONCLUSIONS: This study expands knowledge regarding the molecular basis of PPK, providing important information to aid clinical management in families with PPK from Pakistan.

5.
Ann Hum Genet ; 83(6): 477-482, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31173343

RESUMO

Ciliopathies are a clinically and genetically heterogeneous group of disorders often exhibiting phenotypic overlap and caused by abnormalities in the structure or function of cellular cilia. As such, a precise molecular diagnosis is important for guiding clinical management and genetic counseling. In the present study, two Pakistani families comprising individuals with overlapping clinical features suggestive of a ciliopathy syndrome, including intellectual disability, obesity, congenital retinal dystrophy, and hypogonadism (in males), were investigated clinically and genetically. Whole-exome sequencing identified the likely causes of disease as a novel homozygous frameshift mutation (NM_152384.2: c.196delA; p.(Arg66Glufs*12); family 1) in BBS5, and a nonsense mutation (NM_019892.5:c.1879C>T; p.Gln627*; family 2) in INPP5E, previously reported in an extended Pakistani family with MORM syndrome. Our findings expand the molecular spectrum associated with BBS5 mutations in Pakistan and provide further supportive evidence that the INPP5E mutation is a common cause of ciliopathy in Northern Pakistan, likely representing a regional founder mutation. This study also highlights the value of genomic studies in Pakistan for families affected by rare heterogeneous developmental disorders and where clinical phenotyping may be limited by geographical and financial constraints. The identification of the spectrum and frequency of disease-causing variants within this setting enables the development of population-specific genetic testing strategies targeting variants common to the local population and improving health care outcomes.

6.
Genome Res ; 29(7): 1057-1066, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31160375

RESUMO

Germline mutations in fundamental epigenetic regulatory molecules including DNA methyltransferase 3 alpha (DNMT3A) are commonly associated with growth disorders, whereas somatic mutations are often associated with malignancy. We profiled genome-wide DNA methylation patterns in DNMT3A c.2312G > A; p.(Arg771Gln) carriers in a large Amish sibship with Tatton-Brown-Rahman syndrome (TBRS), their mosaic father, and 15 TBRS patients with distinct pathogenic de novo DNMT3A variants. This defined widespread DNA hypomethylation at specific genomic sites enriched at locations annotated as genes involved in morphogenesis, development, differentiation, and malignancy predisposition pathways. TBRS patients also displayed highly accelerated DNA methylation aging. These findings were most marked in a carrier of the AML-associated driver mutation p.Arg882Cys. Our studies additionally defined phenotype-related accelerated and decelerated epigenetic aging in two histone methyltransferase disorders: NSD1 Sotos syndrome overgrowth disorder and KMT2D Kabuki syndrome growth impairment. Together, our findings provide fundamental new insights into aberrant epigenetic mechanisms, the role of epigenetic machinery maintenance, and determinants of biological aging in these growth disorders.

8.
Eye (Lond) ; 33(8): 1339-1346, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30996339

RESUMO

PURPOSE: To investigate eight previously unreported Pakistani families with genetically undefined OCA for mutations in TYR. METHODS: Sanger sequencing of TYR has been performed in eight families with OCA phenotype. Mutation analysis was performed to establish the pathogenic role of novel mutation. Bioinformatics analysis was performed to predict the structural and functional impacts on protein due to the mutation. RESULTS: In this study, we identified six likely pathogenic variants of TYR (c.272 G>A, c.308 G>A, c.346C>T, c.715 C>T, c.832 C>T and c.1255 G>A), including one novel variant (c.308 G>A; p.Cys103Tyr), segregating as appropriate in each family. Cys103 lies in the highly conserved region of the tyrosinase enzyme, and p.Cys103Tyr is predicted to disturb enzymatic function via alteration of the configurational orientation of TYR leading to a more rigid polypeptide structure. We have also reviewed the mutation spectrum of TYR in Pakistani ethnicity. Published data on OCA families proposed that ~40% have been associated with genetic variations in the TYR gene. The mutations reported in this study have now been described with varying frequencies in Pakistani families, including very rare/unique mutations. CONCLUSION: A literature review of TYR gene mutations in Pakistani populations, combined with our genetic data, identified a number of gene mutations likely to represent regional ancestral founder mutations of relevance to Pakistani populations, in addition to sporadic and recurrent 'hotspot' mutations present repeatedly in other regions worldwide.

9.
Eur J Hum Genet ; 27(4): 657-662, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30622327

RESUMO

The centrosomal protein 55 kDa (CEP55 (OMIM 610000)) plays a fundamental role in cell cycle regulation and cytokinesis. However, the precise role of CEP55 in human embryonic growth and development is yet to be fully defined. Here we identified a novel homozygous founder frameshift variant in CEP55, present at low frequency in the Amish community, in two siblings presenting with a lethal foetal disorder. The features of the condition are reminiscent of a Meckel-like syndrome comprising of Potter sequence, hydranencephaly, and cystic dysplastic kidneys. These findings, considered alongside two recent studies of single families reporting loss of function candidate variants in CEP55, confirm disruption of CEP55 function as a cause of this clinical spectrum and enable us to delineate the cardinal clinical features of this disorder, providing important new insights into early human development.

10.
BMC Med Genet ; 19(1): 160, 2018 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-30200890

RESUMO

BACKGROUND: Autosomal recessive anophthalmia and microphthalmia are rare developmental eye defects occurring during early fetal development. Syndromic and non-syndromic forms of anophthalmia and microphthalmia demonstrate extensive genetic and allelic heterogeneity. To date, disease mutations have been identified in 29 causative genes associated with anophthalmia and microphthalmia, with autosomal dominant, autosomal recessive and X-linked inheritance patterns described. Biallelic ALDH1A3 gene variants are the leading genetic causes of autosomal recessive anophthalmia and microphthalmia in countries with frequent parental consanguinity. METHODS: This study describes genetic investigations in two consanguineous Pakistani families with a total of seven affected individuals with bilateral non-syndromic clinical anophthalmia. RESULTS: Using whole exome and Sanger sequencing, we identified two novel homozygous ALDH1A3 sequence variants as likely responsible for the condition in each family; missense mutation [NM_000693.3:c.1240G > C, p.Gly414Arg; Chr15:101447332G > C (GRCh37)] in exon 11 (family 1), and, a frameshift mutation [NM_000693.3:c.172dup, p.Glu58Glyfs*5; Chr15:101425544dup (GRCh37)] in exon 2 predicted to result in protein truncation (family 2). CONCLUSIONS: This study expands the molecular spectrum of pathogenic ALDH1A3 variants associated with anophthalmia and microphthalmia, and provides further insight of the key role of the ALDH1A3 in human eye development.

11.
PLoS Genet ; 14(8): e1007504, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30157172

RESUMO

We identified a homozygous missense alteration (c.75C>A, p.D25E) in CLCC1, encoding a presumptive intracellular chloride channel highly expressed in the retina, associated with autosomal recessive retinitis pigmentosa (arRP) in eight consanguineous families of Pakistani descent. The p.D25E alteration decreased CLCC1 channel function accompanied by accumulation of mutant protein in granules within the ER lumen, while siRNA knockdown of CLCC1 mRNA induced apoptosis in cultured ARPE-19 cells. TALEN KO in zebrafish was lethal 11 days post fertilization. The depressed electroretinogram (ERG) cone response and cone spectral sensitivity of 5 dpf KO zebrafish and reduced eye size, retinal thickness, and expression of rod and cone opsins could be rescued by injection of wild type CLCC1 mRNA. Clcc1+/- KO mice showed decreased ERGs and photoreceptor number. Together these results strongly suggest that intracellular chloride transport by CLCC1 is a critical process in maintaining retinal integrity, and CLCC1 is crucial for survival and function of retinal cells.

12.
Genet Med ; 2018 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-30158690

RESUMO

PURPOSE: Defects in the cohesin pathway are associated with cohesinopathies, notably Cornelia de Lange syndrome (CdLS). We aimed to delineate pathogenic variants in known and candidate cohesinopathy genes from a clinical exome perspective. METHODS: We retrospectively studied patients referred for clinical exome sequencing (CES, N = 10,698). Patients with causative variants in novel or recently described cohesinopathy genes were enrolled for phenotypic characterization. RESULTS: Pathogenic or likely pathogenic single-nucleotide and insertion/deletion variants (SNVs/indels) were identified in established disease genes including NIPBL (N = 5), SMC1A (N = 14), SMC3 (N = 4), RAD21 (N = 2), and HDAC8 (N = 8). The phenotypes in this genetically defined cohort skew towards the mild end of CdLS spectrum as compared with phenotype-driven cohorts. Candidate or recently reported cohesinopathy genes were supported by de novo SNVs/indels in STAG1 (N = 3), STAG2 (N = 5), PDS5A (N = 1), and WAPL (N = 1), and one inherited SNV in PDS5A. We also identified copy-number deletions affecting STAG1 (two de novo, one of unknown inheritance) and STAG2 (one of unknown inheritance). Patients with STAG1 and STAG2 variants presented with overlapping features yet without characteristic facial features of CdLS. CONCLUSION: CES effectively identified disease-causing alleles at the mild end of the cohensinopathy spectrum and enabled characterization of candidate disease genes.

13.
Neurol Genet ; 4(2): e222, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29582019

RESUMO

Objective: To identify the genetic cause of disease in 2 previously unreported families with forms of distal hereditary motor neuropathies (dHMNs). Methods: The first family comprises individuals affected by dHMN type V, which lacks the cardinal clinical feature of vocal cord paralysis characteristic of dHMN-VII observed in the second family. Next-generation sequencing was performed on the proband of each family. Variants were annotated and filtered, initially focusing on genes associated with neuropathy. Candidate variants were further investigated and confirmed by dideoxy sequence analysis and cosegregation studies. Thorough patient phenotyping was completed, comprising clinical history, examination, and neurologic investigation. Results: dHMNs are a heterogeneous group of peripheral motor neuron disorders characterized by length-dependent neuropathy and progressive distal limb muscle weakness and wasting. We previously reported a dominant-negative frameshift mutation located in the concluding exon of the SLC5A7 gene encoding the choline transporter (CHT), leading to protein truncation, as the likely cause of dominantly-inherited dHMN-VII in an extended UK family. In this study, our genetic studies identified distinct heterozygous frameshift mutations located in the last coding exon of SLC5A7, predicted to result in the truncation of the CHT C-terminus, as the likely cause of the condition in each family. Conclusions: This study corroborates C-terminal CHT truncation as a cause of autosomal dominant dHMN, confirming upper limb predominating over lower limb involvement, and broadening the clinical spectrum arising from CHT malfunction.

14.
BMC Med Genet ; 19(1): 25, 2018 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-29458334

RESUMO

BACKGROUND: L-2-hydroxyglutaric aciduria (L2HGA) is a progressive neurometabolic disease of brain caused by mutations of in L-2-hydroxyglutarate dehydrogenase (L2HGDH) gene. Cardinal clinical features include cerebellar ataxia, epilepsy, neurodevelopmental delay, intellectual disability, and other clinical neurological deficits. CASE PRESENTATION: We describe an index case of the family presented with generalised tonic-clonic seizure, developmental delay, intellectual disability, and ataxia. Initially, the differential diagnosis was difficult to be established and a SNP genome wide scan identified the candidate region on chromosome 14q22.1. DNA sequencing showed a novel homozygous mutation in the candidate gene L2HGDH (NM_024884.2: c.178G > A; p.Gly60Arg). The mutation p.Gly60Arg lies in the highly conserved FAD/NAD(P)-binding domain of this mitochondrial enzyme, predicted to disturb enzymatic function. CONCLUSIONS: The combination of homozygosity mapping and DNA sequencing identified a novel mutation in Pakistani family with variable clinical features. This is second report of a mutation in L2HGDH gene from Pakistan and the largest family with L2HGA reported to date.

15.
Brain ; 140(11): 2838-2850, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-29088354

RESUMO

The presynaptic, high-affinity choline transporter is a critical determinant of signalling by the neurotransmitter acetylcholine at both central and peripheral cholinergic synapses, including the neuromuscular junction. Here we describe an autosomal recessive presynaptic congenital myasthenic syndrome presenting with a broad clinical phenotype due to homozygous choline transporter missense mutations. The clinical phenotype ranges from the classical presentation of a congenital myasthenic syndrome in one patient (p.Pro210Leu), to severe neurodevelopmental delay with brain atrophy (p.Ser94Arg) and extend the clinical outcomes to a more severe spectrum with infantile lethality (p.Val112Glu). Cells transfected with mutant transporter construct revealed a virtually complete loss of transport activity that was paralleled by a reduction in transporter cell surface expression. Consistent with these findings, studies to determine the impact of gene mutations on the trafficking of the Caenorhabditis elegans choline transporter orthologue revealed deficits in transporter export to axons and nerve terminals. These findings contrast with our previous findings in autosomal dominant distal hereditary motor neuropathy of a dominant-negative frameshift mutation at the C-terminus of choline transporter that was associated with significantly reduced, but not completely abrogated choline transporter function. Together our findings define divergent neuropathological outcomes arising from different classes of choline transporter mutation with distinct disease processes and modes of inheritance. These findings underscore the essential role played by the choline transporter in sustaining acetylcholine neurotransmission at both central and neuromuscular synapses, with important implications for treatment and drug selection.


Assuntos
Encéfalo/patologia , Mutação de Sentido Incorreto , Síndromes Miastênicas Congênitas/genética , Transtornos do Neurodesenvolvimento/genética , Simportadores/genética , Animais , Animais Geneticamente Modificados , Atrofia , Axônios/metabolismo , Caenorhabditis elegans , Proteínas de Caenorhabditis elegans/genética , Pré-Escolar , Feminino , Células HEK293 , Homozigoto , Humanos , Lactente , Masculino , Proteínas de Membrana Transportadoras/genética , Linhagem , Terminações Pré-Sinápticas/metabolismo , Transporte Proteico , Simportadores/metabolismo
17.
Mol Biol Cell ; 28(19): 2492-2507, 2017 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-28720660

RESUMO

Actin nucleation factors function to organize, shape, and move membrane-bound organelles, yet they remain poorly defined in relation to disease. Galloway-Mowat syndrome (GMS) is an inherited disorder characterized by microcephaly and nephrosis resulting from mutations in the WDR73 gene. This core clinical phenotype appears frequently in the Amish, where virtually all affected individuals harbor homozygous founder mutations in WDR73 as well as the closely linked WHAMM gene, which encodes a nucleation factor. Here we show that patient cells with both mutations exhibit cytoskeletal irregularities and severe defects in autophagy. Reintroduction of wild-type WHAMM restored autophagosomal biogenesis to patient cells, while inactivation of WHAMM in healthy cell lines inhibited lipidation of the autophagosomal protein LC3 and clearance of ubiquitinated protein aggregates. Normal WHAMM function involved binding to the phospholipid PI(3)P and promoting actin nucleation at nascent autophagosomes. These results reveal a cytoskeletal pathway controlling autophagosomal remodeling and illustrate several molecular processes that are perturbed in Amish GMS patients.


Assuntos
Complexo 2-3 de Proteínas Relacionadas à Actina/metabolismo , Amish/genética , Mutação da Fase de Leitura , Proteínas de Membrana/genética , Proteínas Associadas aos Microtúbulos/genética , Fosfatos de Fosfatidilinositol/metabolismo , Complexo 2-3 de Proteínas Relacionadas à Actina/genética , Actinas/metabolismo , Autofagossomos/metabolismo , Autofagossomos/fisiologia , Células Cultivadas , Citoesqueleto/metabolismo , Efeito Fundador , Hérnia Hiatal/genética , Homozigoto , Humanos , Proteínas de Membrana/metabolismo , Microcefalia/genética , Proteínas Associadas aos Microtúbulos/metabolismo , Modelos Moleculares , Nefrose/genética , Fosfatos de Fosfatidilinositol/genética , Proteínas/genética , Proteínas/metabolismo
18.
Brain ; 140(4): 940-952, 2017 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-28334956

RESUMO

PRUNE is a member of the DHH (Asp-His-His) phosphoesterase protein superfamily of molecules important for cell motility, and implicated in cancer progression. Here we investigated multiple families from Oman, India, Iran and Italy with individuals affected by a new autosomal recessive neurodevelopmental and degenerative disorder in which the cardinal features include primary microcephaly and profound global developmental delay. Our genetic studies identified biallelic mutations of PRUNE1 as responsible. Our functional assays of disease-associated variant alleles revealed impaired microtubule polymerization, as well as cell migration and proliferation properties, of mutant PRUNE. Additionally, our studies also highlight a potential new role for PRUNE during microtubule polymerization, which is essential for the cytoskeletal rearrangements that occur during cellular division and proliferation. Together these studies define PRUNE as a molecule fundamental for normal human cortical development and define cellular and clinical consequences associated with PRUNE mutation.


Assuntos
Encéfalo/crescimento & desenvolvimento , Proteínas de Transporte/genética , Deficiências do Desenvolvimento/genética , Microcefalia/genética , Adolescente , Diferenciação Celular/genética , Movimento Celular/genética , Córtex Cerebral/crescimento & desenvolvimento , Criança , Pré-Escolar , Citoesqueleto/genética , Citoesqueleto/ultraestrutura , Feminino , Genes Recessivos , Transtornos Heredodegenerativos do Sistema Nervoso/genética , Humanos , Lactente , Masculino , Microtúbulos/genética , Microtúbulos/ultraestrutura , Mutação/genética , Linhagem , Adulto Jovem
19.
DNA Repair (Amst) ; 50: 22-35, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28073635

RESUMO

Proliferating cell nuclear antigen (PCNA) is an essential cofactor for DNA replication and repair, recruiting multiple proteins to their sites of action. We examined the effects of the PCNAS228I mutation that causes PCNA-associated DNA repair disorder (PARD). Cells from individuals affected by PARD are sensitive to the PCNA inhibitors T3 and T2AA, showing that the S228I mutation has consequences for undamaged cells. Analysis of the binding between PCNA and PCNA-interacting proteins (PIPs) shows that the S228I change dramatically impairs the majority of these interactions, including that of Cdt1, DNMT1, PolD3p66 and PolD4p12. In contrast p21 largely retains the ability to bind PCNAS228I. This property is conferred by the p21 PIP box sequence itself, which is both necessary and sufficient for PCNAS228I binding. Ubiquitination of PCNA is unaffected by the S228I change, which indirectly alters the structure of the inter-domain connecting loop. Despite the dramatic in vitro effects of the PARD mutation on PIP-degron binding, there are only minor alterations to the stability of p21 and Cdt1 in cells from affected individuals. Overall our data suggests that reduced affinity of PCNAS228I for specific clients causes subtle cellular defects in undamaged cells which likely contribute to the etiology of PARD.


Assuntos
Distúrbios no Reparo do DNA/metabolismo , Reparo do DNA , Replicação do DNA , Mutação de Sentido Incorreto , Antígeno Nuclear de Célula em Proliferação/metabolismo , Domínios e Motivos de Interação entre Proteínas/genética , Proteínas de Ciclo Celular/metabolismo , DNA Polimerase III/metabolismo , Humanos , Complexos Multiproteicos , Antígeno Nuclear de Célula em Proliferação/química , Antígeno Nuclear de Célula em Proliferação/genética , Ligação Proteica , Ubiquitinação
20.
Brain ; 140(3): 547-554, 2017 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-28052917

RESUMO

Mutations in genes involved in lipid metabolism have increasingly been associated with various subtypes of hereditary spastic paraplegia, a highly heterogeneous group of neurodegenerative motor neuron disorders characterized by spastic paraparesis. Here, we report an unusual autosomal recessive neurodegenerative condition, best classified as a complicated form of hereditary spastic paraplegia, associated with mutation in the ethanolaminephosphotransferase 1 (EPT1) gene (now known as SELENOI), responsible for the final step in Kennedy pathway forming phosphatidylethanolamine from CDP-ethanolamine. Phosphatidylethanolamine is a glycerophospholipid that, together with phosphatidylcholine, constitutes more than half of the total phospholipids in eukaryotic cell membranes. We determined that the mutation defined dramatically reduces the enzymatic activity of EPT1, thereby hindering the final step in phosphatidylethanolamine synthesis. Additionally, due to central nervous system inaccessibility we undertook quantification of phosphatidylethanolamine levels and species in patient and control blood samples as an indication of liver phosphatidylethanolamine biosynthesis. Although this revealed alteration to levels of specific phosphatidylethanolamine fatty acyl species in patients, overall phosphatidylethanolamine levels were broadly unaffected indicating that in blood EPT1 inactivity may be compensated for, in part, via alternate biochemical pathways. These studies define the first human disorder arising due to defective CDP-ethanolamine biosynthesis and provide new insight into the role of Kennedy pathway components in human neurological function.


Assuntos
Etanolaminofosfotransferase/genética , Etanolaminofosfotransferase/metabolismo , Mutação/genética , Fosfolipídeos/biossíntese , Transdução de Sinais/genética , Paraplegia Espástica Hereditária/genética , Adolescente , Criança , Pré-Escolar , Cromatografia Líquida , Consanguinidade , Análise Mutacional de DNA , Saúde da Família , Feminino , Expressão Gênica , Humanos , Lactente , Masculino , Espectrometria de Massas , Omã , Fosfolipídeos/sangue , Saccharomyces cerevisiae , Paraplegia Espástica Hereditária/diagnóstico por imagem , Paraplegia Espástica Hereditária/enzimologia , Paraplegia Espástica Hereditária/patologia
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