Auditory impairment in H-ABC tubulinopathy

4-aminopyridine improves evoked potentials and ambulation in the taiep rat: A model of hypomyelination with atrophy of basal ganglia and cerebellum

The taiep rat is a tubulin mutant with an early hypomyelination followed by progressive demyelination of the central nervous system due to a point mutation in the Tubb4a gene. It shows clinical, radiological, and pathological signs like those of the human leukodystrophy hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC). Taiep rats had tremor, ataxia, immobility episodes, epilepsy, and paralysis; the acronym of these signs given the name to this autosomal recessive trait. The aim of this study was to analyze the characteristics of somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) in adult taiep rats and in a patient suffering from H-ABC. Additionally, we evaluated the effects of 4-aminopyridine (4-AP) on sensory responses and locomotion and finally, we compared myelin loss in the spinal cord of adult taiep and wild type (WT) rats using immunostaining. Our results showed delayed SSEPs in the upper and the absence of them in the lower extremities in a human patient. In taiep rats SSEPs had a delayed second negative evoked responses and were more susceptible to delayed responses with iterative stimulation with respect to WT. MEPs were produced by bipolar stimulation of the primary motor cortex generating a direct wave in WT rats followed by several indirect waves, but taiep rats had fused MEPs. Importantly, taiep SSEPs improved after systemic administration of 4-AP, a potassium channel blocker, and this drug induced an increase in the horizontal displacement measured in a novelty-induced locomotor test. In taiep subjects have a significant decrease in the immunostaining of myelin in the anterior and ventral funiculi of the lumbar spinal cord with respect to WT rats. In conclusion, evoked potentials are useful to evaluate myelin alterations in a leukodystrophy, which improved after systemic administration of 4-AP. Our results have a translational value because our findings have implications in future medical trials for H-ABC patients or with other leukodystrophies.

Characterization of sperm motility and testosterone secretion in the taiep myelin mutant, a model of demyelination

Presently, demyelinating diseases have been reported to affect the reproductive life of patients who suffer from them, but the progression of the alterations is unknown, especially in men. To better understand these effects, it is necessary to perform studies in animal models, such as the male taiep rat, which exhibits progressive demyelination of the central nervous system, altered kisspeptin expression at the hypothalamic level, and decreased luteinizing hormone, which could alter sperm quality and testicular diameter. Thus, the objective of the present study was to analyze the diameter of the seminiferous tubules, the sperm motility, and the testosterone levels of 90-day-old male taiep rats. The obtained results indicate that male taiep rats show an increase in testicular size accompanied by an increase in the diameter of the seminiferous tubules of the left testicle. There was also a decrease in progressive motility in sperm samples from the left epididymis of male taiep rats compared to the control group, with no changes in serum testosterone concentration. Therefore, we conclude that male taiep rats with central demyelination show altered testicular diameter and decreased motility in sperm from the left side. This type of studies serves as a basis for proposing possible reproductive strategies to improve the fertility and testicular function of men with demyelinating diseases of the central nervous system.

Concurrent optical inspection to boost characterization of plastic cortical bone under mechanical deformation

The simultaneous surface and internal measurements from a chemically modified cortical bovine bone suffering a plastic range deformation are presented. Since the bone is an anisotropic structure, its mechanical response could be modified if its organic or inorganic phases change. The latter could result in high plastic deformations, where the interferometrical signal from an optical analysis is easily de-correlated. In this work, digital holography interferometry (DHI) and Fourier domain optical coherence tomography (FD-OCT) are used to analyze the plastic range deformation of the bone under compression. The simultaneous use of these two optical methods gives information even when one of them de-correlates. The surface results retrieved with DHI show the high anisotropy of the bone as a continuously increasing displacement field map. Meanwhile, the internal information obtained with FD-OCT records larger deformations at different depths. Due to the optical phase, it is possible to complement the measurements of these two methods during the plastic deformation.

H-ABC tubulinopathy revealed by label-free second harmonic generation microscopy

Hypomyelination with atrophy of the basal ganglia and cerebellum is a recently described tubulinopathy caused by a mutation in the tubulin beta 4a isoform, expressed in oligodendrocytes. The taiep rat is the only spontaneous tubulin beta 4a mutant available for the study of this pathology. We aimed to identify the effects of the tubulin mutation on freshly collected, unstained samples of the central white matter of taiep rats using second harmonic generation microscopy. Cytoskeletal differences between the central white matter of taiep rats and control animals were found. Nonlinear emissions from the processes and somata of oligodendrocytes in tubulin beta 4a mutant rats were consistently detected, in the shape of elongated structures and cell-like bodies, which were never detected in the controls. This signal represents the second harmonic trademark of the disease. The tissue was also fluorescently labeled and analyzed to corroborate the origin of the nonlinear signal. Besides enabling the description of structural and molecular aspects of H-ABC, our data open the door to the diagnostic use of nonlinear optics in the study of neurodegenerative diseases, with the additional advantage of a label-free approach that preserves tissue morphology and vitality.

Longitudinal Evaluation of Cerebellar Signs of H-ABC Tubulinopathy in a Patient and in the taiep Model

Hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC) is a central neurodegenerative disease due to mutations in the tubulin beta-4A (TUBB4A) gene, characterized by motor development delay, abnormal movements, ataxia, spasticity, dysarthria, and cognitive deficits. Diagnosis is made by integrating clinical data and radiological signs. Differences in MRIs have been reported in patients that carry the same mutation; however, a quantitative study has not been performed so far. Our study aimed to provide a longitudinal analysis of the changes in the cerebellum (Cb), corpus callosum (CC), ventricular system, and striatum in a patient suffering from H-ABC and in the taiep rat. We correlated the MRI signs of the patient with the results of immunofluorescence, gait analysis, segmentation of cerebellum, CC, and ventricular system, performed in the taiep rat. We found that cerebellar and callosal changes, suggesting a potential hypomyelination, worsened with age, in concomitance with the emergence of ataxic gait. We also observed a progressive lateral ventriculomegaly in both patient and taiep, possibly secondary to the atrophy of the white matter. These white matter changes are progressive and can be involved in the clinical deterioration. Hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC) gives rise to a spectrum of clinical signs whose pathophysiology still needs to be understood.

Long-term taurine administration improves motor skills in a tubulinopathy rat model by decreasing oxidative stress and promoting myelination

The taiep rat undergoes hypomyelination and progressive demyelination caused by an abnormal microtubule accumulation in oligodendrocytes, which elicits neuroinflammation and motor behavior dysfunction. Based on taurine antioxidant and proliferative actions, this work explored whether its sustained administration from the embryonic age to adulthood could prevent neuroinflammation, stimulate cell proliferation, promote myelination, and relieve motor impairment. Taurine (50 mg/L of drinking water = 50 ppm) was given to taiep pregnant rats on gestational day 15 and afterward to the male offspring until eight months of age. We measured the levels of nitric oxide (NO), malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA), CXCL1, CXCR2 receptor, growth factors (BNDF and FGF2), cell proliferation, and myelin content over time. Integral motor behavior was also evaluated. Our results showed that taurine administration significantly decreased NO and MDA + 4-HDA levels, increased cell proliferation, and promoted myelination in an age- and brain region-dependent fashion compared with untreated taiep rats. Taurine effect on chemokines and growth factors was also variable. Taurine improved vestibular reflexes and limb muscular strength in perinatal rats and fine movements and immobility episodes in adult rats. These results show that chronic taurine administration partially alleviates the taiep neuropathology.