Search

Scleroderma is a chronic autoimmune connective tissue disease of unknown etiology characterized by excessive fibrosis and is broadly divided into two clinical entities: localized scleroderma (LSc) and systemic sclerosis (SSc). SSc is a multi-system disease resulting in both skin and visceral organ fibrosis. The more benign disorder, LSc is for the most part self-limited with the disease pathology being confined to the skin and subcutaneous tissues. Proposed factors involved in the pathogenesis of these disorders include endothelial cell injury and dysfunction, immunological alterations and inflammatory activation, and abnormal ECM production by activated fibroblasts. However, the initiating mechanisms that leads to these changes remains largely unknown. This thesis examines the hypothesis that the transcriptional expression at the edge and centre of expanding LSc plaques could represent the metabolic changes involved in the different stages of disease. The major finding of this thesis was the identification of two panels of genes that showed significant changes in expression between LSc patients and healthy controls irrespective of whether the sample was taken from a diseased or clinically unaffected area of the patient. The first panel consisted of inflammatory genes including those genes characteristic of the Thl response and those induced by NF-KB. The Thl response was supported by an increased infiltration of CD4+ T cells in the LSc patients. The second panel consisted of a subset of array identified genes (scleroderma Signature) in SSc patients. Of interest, WIF1 was down regulated in both disorders and showed a gradual decrease in expression across the clinically different areas of the LSc patients. Both panels of genes showed the biggest changes of expression at the edge of the plaque suggesting their involvement in the initiating events of the disease. These results suggest that, like SSc, the underlying pathology of LSc is related to systemic changes in genes controlling amongst others, immunological and inflammatory responses. This information not only sheds light on the mechanisms involved in the initiation and progression of scleroderma, but could also contribute to the creation of a diagnostic test for the early detection of sufferers of this rare, but important disease.

Childhood onset motor neuron diseases or neuronopathies are a clinically heterogeneous group of disorders. A particularly severe subgroup first described in 1894, and subsequently called Brown-Vialetto-Van Laere syndrome, is characterized by progressive pontobulbar palsy, sensorineural hearing loss and respiratory insufficiency. There has been no treatment for this progressive neurodegenerative disorder, which leads to respiratory failure and usually death during childhood. We recently reported the identification of SLC52A2, encoding riboflavin transporter RFVT2, as a new causative gene for Brown-Vialetto-Van Laere syndrome. We used both exome and Sanger sequencing to identify SLC52A2 mutations in patients presenting with cranial neuropathies and sensorimotor neuropathy with or without respiratory insufficiency. We undertook clinical, neurophysiological and biochemical characterization of patients with mutations in SLC52A2, functionally analysed the most prevalent mutations and initiated a regimen of high-dose oral riboflavin. We identified 18 patients from 13 families with compound heterozygous or homozygous mutations in SLC52A2. Affected individuals share a core phenotype of rapidly progressive axonal sensorimotor neuropathy (manifesting with sensory ataxia, severe weakness of the upper limbs and axial muscles with distinctly preserved strength of the lower limbs), hearing loss, optic atrophy and respiratory insufficiency. We demonstrate that SLC52A2 mutations cause reduced riboflavin uptake and reduced riboflavin transporter protein expression, and we report the response to high-dose oral riboflavin therapy in patients with SLC52A2 mutations, including significant and sustained clinical and biochemical improvements in two patients and preliminary clinical response data in 13 patients with associated biochemical improvements in 10 patients. The clinical and biochemical responses of this SLC52A2-specific cohort suggest that riboflavin supplementation can ameliorate the progression of this neurodegenerative condition, particularly when initiated soon after the onset of symptoms.

Defects in the motor domain of kinesin family member 1A (KIF1A), a neuron-specific ATP-dependent anterograde axonal transporter of synaptic cargo, are well-recognized to cause a spectrum of neurological conditions, commonly known as KIF1A-associated neurological disorders (KAND). Here we report one mutation-negative female with classic Rett syndrome (RTT) harboring a de novo heterozygous novel variant [NP_001230937.1:p.(Asp248Glu)] in the highly-conserved motor domain of KIF1A. In addition, three individuals with severe neurodevelopmental disorder along with clinical features overlapping with KAND are also reported carrying de novo heterozygous novel [NP_001230937.1:p.(Cys92Arg) & p.(Pro305Leu)] or previously reported [NP_001230937.1:p.(Thr99Met)] variants in KIF1A. In silico tools predicted these variants to be likely pathogenic, and 3D molecular modelling predicted defective ATP hydrolysis and/or microtubule binding. Using the neurite tip accumulation assay, we demonstrated that all novel KIF1A variants significantly reduced the ability of the motor domain of KIF1A to accumulate along neurite lengths of differentiated SH-SY5Y cells. In vitro microtubule gliding assays showed significantly reduced velocities for the variant p.(Asp248Glu) and reduced microtubule binding for the p.(Cys92Arg) and p.(Pro305Leu) variants, suggesting decreased ability of KIF1A to move along microtubules. Thus, this study further expanded the phenotypic characteristics of KAND individuals with pathogenic variants in KIF1A motor domain to include clinical features commonly seen in RTT individuals. This article is protected by copyright. All rights reserved.