Axon Transport and Neuropathy: Relevant Perspectives on the Etiopathogenesis of Familial Dysautonomia.

Peripheral neuropathies are highly prevalent and are most often associated with chronic disease, side effects from chemotherapy, or toxic-metabolic abnormalities. Neuropathies are less commonly caused by genetic mutations, but studies of the normal function of mutated proteins have identified particular vulnerabilities that often implicate mitochondrial dynamics and axon transport mechanisms. Hereditary sensory and autonomic neuropathies are a group of phenotypically related diseases caused by monogenic mutations that primarily affect sympathetic and sensory neurons. Here, I review evidence to indicate that many genetic neuropathies are caused by abnormalities in axon transport. Moreover, in hereditary sensory and autonomic neuropathies. There may be specific convergence on gene mutations that disrupt nerve growth factor signaling, upon which sympathetic and sensory neurons critically depend.

Advances in Experimental Neuropathology: New Methods and Insights.

This Editorial introduces this month's special Neuropathology Theme Issue, a series of Reviews on advances in our understanding of rare human hereditary neuropathies, peripheral nervous system tumors, and common degenerative diseases.

Afferent baroreflex failure in familial dysautonomia.

BACKGROUND: Familial dysautonomia (FD) is due to a genetic deficiency of the protein IKAP, which affects development of peripheral neurons. Patients with FD display complex abnormalities of the baroreflex of unknown cause. METHODS: To test the hypothesis that the autonomic phenotype of FD is due to selective impairment of afferent baroreceptor input, we examined the autonomic and neuroendocrine responses triggered by stimuli that either engage (postural changes) or bypass (cognitive/emotional) afferent baroreflex pathways in 50 patients with FD and compared them to those of normal subjects and to those of patients with pure autonomic failure (PAF), a disorder with selective impairment of efferent autonomic neurons. RESULTS: During upright tilt, in patients with FD and in patients with PAF blood pressure fell markedly but the heart rate increased in PAF and decreased in FD. Plasma norepinephrine levels failed to increase in both groups. Vasopressin levels increased appropriately in patients with PAF but failed to increase in patients with FD. Head-down tilt increased blood pressure in both groups but increased heart rate only in patients with FD. Mental stress evoked a marked increase in blood pressure and heart rate in patients with FD but little change in those with PAF. CONCLUSION: The failure to modulate sympathetic activity and to release vasopressin by baroreflex-mediated stimuli together with marked sympathetic activation during cognitive tasks indicate selective failure of baroreceptor afference. These findings indicate that IKAP is critical for the development of afferent baroreflex pathways and has therapeutic implications in the management of these patients.

Transcription impairment and cell migration defects in elongator-depleted cells: implication for familial dysautonomia.

Mutations in IKBKAP, encoding a subunit of Elongator, cause familial dysautonomia (FD), a severe neurodevelopmental disease with complex clinical characteristics. Elongator was previously linked not only with transcriptional elongation and histone acetylation but also with other cellular processes. Here, we used RNA interference (RNAi) and fibroblasts from FD patients to identify Elongator target genes and study the role of Elongator in transcription. Strikingly, whereas Elongator is recruited to both target and nontarget genes, only target genes display histone H3 hypoacetylation and progressively lower RNAPII density through the coding region in FD cells. Interestingly, several target genes encode proteins implicated in cell motility. Indeed, characterization of IKAP/hELP1 RNAi cells, FD fibroblasts, and neuronal cell-derived cells uncovered defects in this cellular function upon Elongator depletion. These results indicate that defects in Elongator function affect transcriptional elongation of several genes and that the ensuing cell motility deficiencies may underlie the neuropathology of FD patients.

Alpha-catulin maps to the familial dysautonomia region on 9q31.

Familial dysautonomia is a severe autosomal-recessive neurodegenerative disease that primarily affects the Ashkenazi Jewish population. We present the mapping of alpha-catulin and show that it maps precisely to the familial dysautonomia candidate region on 9q31. Patient sequence analysis identified two new sequence variants, which show linkage disequilibrium with this disease. A G to A transition at nucleotide 423 in exon 3 is a silent base change that does not alter the Val residue at position 141. A G to C transversion at nucleotide 1579 changes the Glu at postion 527 to Gln. These base changes were analyzed in several patients, unaffected Ashkenazi Jewish controls, and non-Jewish controls. Because of the presence of these sequence variants in several unaffected individuals, alpha-catulin is unlikely to be the causative gene in this disease.

The Riley-Day syndrome. Familial dysautonomy, central autonomic dysfunction.

The Riley-Day syndrome is characterized by a dysfunction of the autonomous nervous system, sensory disturbances, neurological disorders, psychical anomalies and important ophthalmological symptoms, such as absence of tears, corneal anaesthesia, keratinized conjunctiva and cornea; myosis after instillation of methacholine. The diagnosis is based on the absence of fungiform papillae of the tongue and the absence of reaction after intradermic injection of histamine. The inheritance is autosomal recessive. The disease results probably from an enzymatic insufficiency.

[Dysautonomia in acute primary polyradiculoneuritis]. / La dysautonomie des polyradiculonévrites aiguës primitives

In this research involving 172 cases of acute primary polyradiculoneuritis, the authors draw attention to the frequency and seriousness of the autonomic disorders, notably circulatory disorders (arterial hypertension, bradycardia), water retention, disorders in glucose metabolism. They have found a close correlation between the development of arterial hypertension and levels of VMA and the cathecholamines and between the appearance of hyperglycaemia and the level of urinary 17 OH. Free water clearance is often negative and becomes positive as the paralytic syndrome improves. The biological picture is identical with that brought about by inappropriate secretion of HAD. From the therapeutic point of view, caution is advised in using certain procedures and in prescribing certain drugs.

Acute autonomic neuropathy. Its occurrence in infectious mononucleosis.

A 13-year-old girl with acute onset of symptoms limited to autonomic dysfunction was found to be suffering from infectious mononucleosis. With symptomatic therapy, improvement gradually occurred over a period of seven months. The documentation of this case widens the spectrum of disorders to be considered as a cause of so-called acute pandysautonomia or autonomic neuropathy.