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Abetalipoproteinemia (ABL) is a rare monogenic disease characterized by very low plasma levels of cholesterol and triglyceride and almost complete absence of apolipoprotein B (apoB)-containing lipoproteins. Typically, patients present with failure to thrive, acanthocytosis, pigmented retinopathy and neurological features. It has been shown that ABL results from mutations in the gene encoding the microsomal triglyceride transfer protein (MTTP). Sanger sequencing of MTTP was performed for two unrelated consanguineous Tunisian families with two affected individuals each, presenting a more severe ABL phenotype than previously reported in the literature. The patients were found to be homozygous for two novel mutations. In the first family, a nonsense mutation, c.2313T>A, leading to a truncated protein (p.Y771X) was identified. In the second family, a splice mutation, IVS 9+2T>G, was found. These mutations are believed to abolish the assembly and secretion of apoB-containing lipoproteins.

Background: Autosomal recessive cerebellar ataxias (ARCA) are a complex group of neurodegenerative disorders with high clinical and genetic heterogeneity. In most cases, the cerebellar ataxia is not pure, and complicating clinical features such as pyramidal signs or extraneurological features are found. Objective: To identify the genetic origin of the cerebellar ataxia for 3 consanguineous North African families presenting with ARCA. Methods: Genome-wide high-density SNP genotyping and whole-exome sequencing were performed followed by Sanger sequencing for mutation confirmation. Results: Two variants were identified in SLC25A46. Mutations in this gene have been previously associated with Charcot-Marie-Tooth type 2 and optic atrophy. While the previously reported variant p.Arg340Cys seems to be consistently associated with the same clinical features such as childhood onset, optic atrophy, gait and speech difficulties, and wasting of the lower limbs, the patient with the novel mutation p.Trp160Ser did not present with optic atrophy and his ocular abnormalities were limited to nystagmus and saccadic pursuit. Conclusion: In this study, we report a novel variant (p.Trp160Ser) in SLC25A46 and we broaden the phenotypic spectrum associated with mutations in SLC25A46.

Horizontal gaze palsy with progressive scoliosis (HGPPS) is a rare autosomal recessive disorder characterized by the congenital absence of horizontal gaze, progressive scoliosis, and failure of the corticospinal and somatosensory axon tracts to decussate in the medulla. HGPPS is caused by mutations of the ROBO3 gene, which encodes a protein that shares homology with the roundabout family of transmembrane receptors that are important in axon guidance and neuronal migration. To date, over 15 mutations have been found in consanguineous families of Greek, Italian, Turkish, Pakistani, Saudi Arabian, and Indian descent. To detail clinical, cerebral magnetic resonance imaging (MRI) and genetic findings of ten HGPPS patients from four unrelated Tunisian families. Four unrelated consanguineous Tunisian families with a total of ten patients suffering from horizontal gaze palsy with progressive scoliosis. Genetic linkage analysis and direct sequencing of the ROBO3 gene. All patients shared similar clinical gaze movement abnormalities and variable degrees of scoliosis. Four distinct homozygous mutations were identified. This study extends the molecular spectrum of the ROBO3 gene and the geographic origin of patients with ROBO3 gene mutations, and underlines the homogeneity of the motor ocular syndrome whatever type of mutation is encountered.