1. Bi-allelic LETM1 variants perturb mitochondrial ion homeostasis leading to a clinical spectrum with predominant nervous system involvement
- Author
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Kaiyrzhanov, R., Mohammed, S.E.M., Maroofian, R., Husain, R.A., Catania, A., Torraco, A., Alahmad, A., Dutra-Clarke, M., Grønborg, S., Sudarsanam, A., Vogt, J., Arrigoni, F., Baptista, J., Haider, S., Feichtinger, R.G., Bernardi, P., Zulian, A., Gusic, M., Efthymiou, S., Bai, R., Bibi, F., Horga, A., Martinez-Agosto, J.A., Lam, A., Manole, A, Rodriguez, D.P., Durigon, R., Pyle, A., Albash, B., Dionisi-Vici, C., Murphy, D., Martinelli, D., Bugiardini, E., Allis, K., Lamperti, C., Reipert, S., Risom, L., Laugwitz, L., Nottia, M. Di, McFarland, R., Vilarinho, L., Hanna, M., Prokisch, H., Mayr, J.A., Bertini, E.S., Ghezzi, D., Østergaard, E., Wortmann, S.B., Carrozzo, R., Haack, T.B., Taylor, R.W., Spinazzola, A., Nowikovsky, K., Houlden, H., Kaiyrzhanov, R., Mohammed, S.E.M., Maroofian, R., Husain, R.A., Catania, A., Torraco, A., Alahmad, A., Dutra-Clarke, M., Grønborg, S., Sudarsanam, A., Vogt, J., Arrigoni, F., Baptista, J., Haider, S., Feichtinger, R.G., Bernardi, P., Zulian, A., Gusic, M., Efthymiou, S., Bai, R., Bibi, F., Horga, A., Martinez-Agosto, J.A., Lam, A., Manole, A, Rodriguez, D.P., Durigon, R., Pyle, A., Albash, B., Dionisi-Vici, C., Murphy, D., Martinelli, D., Bugiardini, E., Allis, K., Lamperti, C., Reipert, S., Risom, L., Laugwitz, L., Nottia, M. Di, McFarland, R., Vilarinho, L., Hanna, M., Prokisch, H., Mayr, J.A., Bertini, E.S., Ghezzi, D., Østergaard, E., Wortmann, S.B., Carrozzo, R., Haack, T.B., Taylor, R.W., Spinazzola, A., Nowikovsky, K., and Houlden, H.
- Abstract
Contains fulltext : 283148.pdf (Publisher’s version ) (Open Access), Leucine zipper-EF-hand containing transmembrane protein 1 (LETM1) encodes an inner mitochondrial membrane protein with an osmoregulatory function controlling mitochondrial volume and ion homeostasis. The putative association of LETM1 with a human disease was initially suggested in Wolf-Hirschhorn syndrome, a disorder that results from de novo monoallelic deletion of chromosome 4p16.3, a region encompassing LETM1. Utilizing exome sequencing and international gene-matching efforts, we have identified 18 affected individuals from 11 unrelated families harboring ultra-rare bi-allelic missense and loss-of-function LETM1 variants and clinical presentations highly suggestive of mitochondrial disease. These manifested as a spectrum of predominantly infantile-onset (14/18, 78%) and variably progressive neurological, metabolic, and dysmorphic symptoms, plus multiple organ dysfunction associated with neurodegeneration. The common features included respiratory chain complex deficiencies (100%), global developmental delay (94%), optic atrophy (83%), sensorineural hearing loss (78%), and cerebellar ataxia (78%) followed by epilepsy (67%), spasticity (53%), and myopathy (50%). Other features included bilateral cataracts (42%), cardiomyopathy (36%), and diabetes (27%). To better understand the pathogenic mechanism of the identified LETM1 variants, we performed biochemical and morphological studies on mitochondrial K(+)/H(+) exchange activity, proteins, and shape in proband-derived fibroblasts and muscles and in Saccharomyces cerevisiae, which is an important model organism for mitochondrial osmotic regulation. Our results demonstrate that bi-allelic LETM1 variants are associated with defective mitochondrial K(+) efflux, swollen mitochondrial matrix structures, and loss of important mitochondrial oxidative phosphorylation protein components, thus highlighting the implication of perturbed mitochondrial osmoregulation caused by LETM1 variants in neurological and mitochondrial patholog
- Published
- 2022