Identificación de las bases genéticas de la discinesia paroxística

1 página. IX Jornadas Andaluzas de Salud Investiga. Cádiz 20-22 octubre, 2010.La Discinesia Paroxística Cinesigénica (PKD) es un trastorno del movimiento, caracterizado por movimientos involuntarios episódicos y repentinos, desencadenados por movimientos bruscos. Los distintos tipos de discinesia paroxística muestran un elevado grado de solapa-miento en su presentación clínica. Los estudios genéticos han demostrado, además, la existencia de heterogeneidad genética. En este estudio proponemos identificar los genes causantes de PKD en dos familias independientes.Peer reviewe

Mutation p.Arg324Thr in the KCNA1 gene alters Kv1.1 channel function in a family with episodic ataxia

Póster presentado en la 5th Spanish Ion Channel Network Meeting (RECI V), celebrada en Barcelona del 4 al 6 de octubre de 2015.Episodic ataxia (EA) is a rare autosomal dominant neurological disorder characterized by brief episodes of cerebellar dysfunction and myokymia or neuromyotonia. We recruited the participation of a family with 5 affected members with a diagnosis of paroxysmal kinesigenic dyskinesia vs episodic ataxia with secondarily generalized epilepsy. The age of onset ranged from 3 to 6 years. The patients had brief episodes (C, p.Arg324Thr. The affected residue is located within the cytoplasmic loop between S4 and S5 of the Kv1.1 channel. The mutation cosegregates with the disease and it is absent from 622 control chromosomes. To study whether the mutation altered the channel biophysical properties, the wild type (WT), heterozygous (WT:R324T) and mutant (R324T) channels were expressed in HEK-293T cells. When compared to the WT channel, the WT:R324T and R324T channels: i) produced significantly smaller currents; ii) activated at more positive potentials (~10 and ~20 mV, respectively) and with significantly slower kinetics; and iii) showed a depolarizing shift (~10 and ~20 mV, respectively) in the voltage dependence of the steady-state inactivation. Taken together, the data reported here support the relevance of the KCNA1 gene in EA and the role of the p.Arg324Thr mutation in the channel kinetics.Peer Reviewe

Identification of causative and susceptibility variants in the neurexin-neuroligin pathway in patients with Alzheimer's disease. The role of a truncating mutation in Neuroligin 1

Póster presentado en el 16th National Congress of the Spanish Society of Neuroscience (SENC 2015), celebrado el Granada del 23 al 25 de septiembre de 2015.Neurexins (NRXN) and neuroligins (NLGN) are synaptic cell-adhesion proteins involved in neurodevelopmental disorders, as autism and intellectual disability. Previously, we have postulated a role of NRNX-NLGN in Alzheimer's disease (AD). Here, we present genetic and functional approaches to identify variants of the NRNX-NLGN pathway in AD patients. Using next-generation sequencing, we have studied a panel of 36 genes of the NRNX-NLGN synaptic pathway in 192 AD patients. Potential causal variants were studied by in silico analysis and validated by Sanger sequencing. Susceptibility variants were analyzed by manual inspection in IGV (Integrative Genomics Viewer). Functional studies of selected variants were performed in N2A and COS cells and cultured hipocampal neurons. To identify susceptibility alleles, we selected SNPs whose allelic frequency differed among the genotyped AD patients and the control databases. These SNPs were then genotyped in a geographically-matched control population. On the other hand, potential causative mutations were selected among novel variants with a predicted pathogenic effect. We present a two base-pair insertion in NLGN1 (p.Thr271fs) in a patient with familial history of AD. The frameshift mutation in NLGN1 predicts a premature STOP codon that truncates the extracellular domain. We generated expression vectors for the p.Thr271fs mutation. In western blot experiments we detected a band of ~130 kD corresponding to wild type NLGN1. In contrast, the p.Thr271fs mutation resulted in truncated proteins of ~30 kDa. Localization studies in COS cells showed that p.Thr271fs NLGN1 failed to reach the plasma membrane and accumulated in the ER. In neurons, NLGN1 induces the formation of glutamatergic synapses. We showed that p.Thr271fs NLGN1 failed to induce the formation of glutamatergic synapses and accumulated in the soma of transfected neurons. Thus, the synaptic activity of NLGN1 was abolished by the AD-associated p.Thr271fs mutation. Our data report the first inactivating mutation in the NLGN1 gene in AD patients and support a role for the NRXN-NLGN pathway in the etiology of AD.Peer Reviewe

The H syndrome: Two novel mutations affecting the same amino acid residue of hENT3

3 páginas, 2 figuras.H syndrome (OMIM 612391) is a recently described autosomal-recessive genodermatosis with systemic manifestations. The disease is characterized by the major clinical findings of progressive cutaneous hyperpigmentation and hypertrichosis located mainly over the lower limbs and lower abdomen, hepatosplenomegaly, heart anomalies, hearing loss, hypogonadism, low height and hyperglycemia/diabetes mellitus [1] and [2]. The major histopathological findings include dermal infiltrate consisting mainly of histiocytes, later replaced by dermal and subcutaneous fibrosis [3]. Recently, we [2] and others [4] found that missense, nonsense, compound and deletion mutations in the SLC29A3 gene are responsible for this unique clinical picture. The SLC29A3 gene encodes the human equilibrative nucleoside transporter (hENT3), which mediates passive sodium-independent transport of nucleosides [5]. The exact cellular localization of hENT3, endosomal/lysosomal [6] or mitochondrial [7], and its function with relation to the H syndrome is still unclear. Here, we report two new cases of H syndrome, of Spanish and of Arab origin and describe two novel missense mutations.Authority for Research and Development, Hebrew University of Jerusalem (A.Z.), the Hadassah Medical Center physician scientist program and the Hadassah-Hebrew University Joint Research Fund (V.M.P.)Peer reviewe

A truncating mutation in Alzheimer's disease inactivates neuroligin-1 synaptic function

Neuroligins (NLs) are cell-adhesion proteins that regulate synapse formation and function. Neuroligin 1 (NL1) promotes the formation of glutamatergic synapses and mediates long-term potentiation in mouse models. Thus, altered NL1 function could mediate the synaptic and memory deficits associated with Alzheimer's disease (AD). Here, we describe a frameshift mutation, c.875_876insTT, in the neuroligin 1 gene (NLGN1) in a patient with AD and familial history of AD. The insertion generates a premature stop codon in the extracellular domain of NL1 (p.Thr271fs). Expression of mutant NL1 shows accumulation of truncated NL1 proteins in the endoplasmic reticulum. In hippocampal neurons, the p.Thr271fs mutation abolishes the ability of NL1 to promote the formation of glutamatergic synapses. Our data support a role for inactivating mutations in NLGN1 in AD. Previous studies have reported rare mutations in X-linked NLGNL3 and NLGNL4 genes in patients with autism, which result in the inactivation of the mutant alleles. Therefore, together with a role in neurodevelopmental disorders, altered NL function could underlie the molecular mechanisms associated with brain diseases in the elderly.This work was funded by grants from Junta de Andalucía (P11-CVI-7599) and Instituto de Salud Carlos III (PI11/1058).Peer Reviewe

A novel MYH7 founder mutation causing Laing distal myopathy in Southern Spain.

MYH7 gene mutations are associated with wide clinical and genetic heterogeneity. We report a novel founder mutation in MYH7 in Southern Spain (Andalucía). We studied two index patients and 24 family members from two apparently independent families by physical examination, serum creatine-kinase, muscle MRI, sequencing studies and genetic linkage analysis. Sixteen individuals were heterozygous for a (p.R1560P) variant in the MYH7 gene. Haplotype was consistent with a common ancestor for the two families. The patients displayed the classic Laing distal myopathy phenotype, with hanging first toe as the initial presentation, even in mildly affected patients who declared themselves asymptomatic, although neck flexor weakness was revealed as an early sign in some cases. MRI showed that the sartorius was the first muscle involved, even in two out of three asymptomatic carriers. Our findings support the novel variant p.R1560P in MYH7 as a founder mutation in Andalucía. The early involvement of the sartorius muscle in MRI may be useful as an indicator of affection status