Congenital Insensitivity to Pain: Novel SCN9A Missense and In-Frame Deletion Mutations

SCN9A encodes the voltage-gated sodium channel Nav1.7, a protein highly expressed in pain-sensing neurons. Mutations in SCN9A cause three human pain disorders: bi-allelic loss of function mutations result in Channelopathy-associated Insensitivity to Pain (CIP), whereas activating mutations cause severe episodic pain in Paroxysmal Extreme Pain Disorder (PEPD) and Primary Erythermalgia (PE). To date, all mutations in SCN9A that cause a complete inability to experience pain are protein truncating and presumably lead to no protein being produced. Here, we describe the identification and functional characterization of two novel non-truncating mutations in families with CIP: a homozygously-inherited missense mutation found in a consanguineous Israeli Bedouin family (Nav1.7-R896Q) and a five amino acid in-frame deletion found in a sporadic compound heterozygote (Nav1.7-ΔR1370-L1374). Both of these mutations map to the pore region of the Nav1.7 sodium channel. Using transient transfection of PC12 cells we found a significant reduction in membrane localization of the mutant protein compared to the wild type. Furthermore, voltage clamp experiments of mutant-transfected HEK293 cells show a complete loss of function of the sodium channel, consistent with the absence of pain phenotype. In summary, this study has identified critical amino acids needed for the normal subcellular localization and function of Nav1.7. © 2010 Wiley-Liss, Inc

Correlates of Caregiving Burden among Bedouin-Muslim Mothers of Children Diagnosed with Epilepsy

A paucity of research exists on caregiving burden (CB) and the factors associated with it among minority groups, such as Bedouin mothers of children diagnosed with epilepsy (CDE). The aim of this study was to explore associations between CB and care-recipients’ characteristics, contextual factors, and caregivers’ characteristics among those mothers. Methods: A total of 50 mothers completed self-report questionnaires while visiting pediatric neurology outpatient clinic centers, using valid and reliable measures. Results: Bivariate associations were found between social support, number of medications, and CB. General self-efficacy and place of residence emerged as significant predictors of caregiver burden. Conclusions: These findings provide health professionals with a better understanding of the factors that should be assessed in order to address caregiver burden among Bedouin mothers of CDE. Understanding the unique characteristics and culture of the Bedouin community can help professionals in targeting caregivers with a lower sense of self-efficacy, and those that reside in Bedouin cities, in order to reduce their caregiving burden

PLA2G6 Mutation Underlies Infantile Neuroaxonal Dystrophy

Infantile neuroaxonal dystrophy (INAD) is an autosomal recessive progressive neurodegenerative disease that presents within the first 2 years of life and culminates in death by age 10 years. Affected individuals from two unrelated Bedouin Israeli kindreds were studied. Brain imaging demonstrated diffuse cerebellar atrophy and abnormal iron deposition in the medial and lateral globus pallidum. Progressive white-matter disease and reduction of the N-acetyl aspartate:chromium ratio were evident on magnetic resonance spectroscopy, suggesting loss of myelination. The clinical and radiological diagnosis of INAD was verified by sural nerve biopsy. The disease gene was mapped to a 1.17-Mb locus on chromosome 22q13.1 (LOD score 4.7 at recombination fraction 0 for SNP rs139897), and an underlying mutation common to both affected families was identified in PLA2G6, the gene encoding phospholipase A2 group VI (cytosolic, calcium-independent). These findings highlight a role of phospholipase in neurodegenerative disorders