Sunday, April 21, 2024

SPATA5L1(AFG2B) mutations

Inspired by a patient

Richard EM, Bakhtiari S, Marsh APL, Kaiyrzhanov R, Wagner M, Shetty S, Pagnozzi A, Nordlie SM, Guida BS, Cornejo P, Magee H, Liu J, Norton BY, Webster RI, Worgan L, Hakonarson H, Li J, Guo Y, Jain M, Blesson A, Rodan LH, Abbott MA, Comi A, Cohen JS, Alhaddad B, Meitinger T, Lenz D, Ziegler A, Kotzaeridou U, Brunet T, Chassevent A, Smith-Hicks C, Ekstein J, Weiden T, Hahn A, Zharkinbekova N, Turnpenny P, Tucci A, Yelton M, Horvath R, Gungor S, Hiz S, Oktay Y, Lochmuller H, Zollino M, Morleo M, Marangi G, Nigro V, Torella A, Pinelli M, Amenta S, Husain RA, Grossmann B, Rapp M, Steen C, Marquardt I, Grimmel M, Grasshoff U, Korenke GC, Owczarek-Lipska M, Neidhardt J, Radio FC, Mancini C, Claps Sepulveda DJ, McWalter K, Begtrup A, Crunk A, Guillen Sacoto MJ, Person R, Schnur RE, Mancardi MM, Kreuder F, Striano P, Zara F, Chung WK, Marks WA, van Eyk CL, Webber DL, Corbett MA, Harper K, Berry JG, MacLennan AH, Gecz J, Tartaglia M, Salpietro V, Christodoulou J, Kaslin J, Padilla-Lopez S, Bilguvar K, Munchau A, Ahmed ZM, Hufnagel RB, Fahey MC, Maroofian R, Houlden H, Sticht H, Mane SM, Rad A, Vona B, Jin SC, Haack TB, Makowski C, Hirsch Y, Riazuddin S, Kruer MC. Bi-allelic variants in SPATA5L1 lead to intellectual disability, spastic-dystonic cerebral palsy, epilepsy, and hearing loss. Am J Hum Genet. 2021 Oct 7;108(10):2006-2016. doi: 10.1016/j.ajhg.2021.08.003. PMID: 34626583; PMCID: PMC8546233.


Spermatogenesis-associated 5 like 1 (SPATA5L1) represents an orphan gene encoding a protein of unknown function. We report 28 bi-allelic variants in SPATA5L1 associated with sensorineural hearing loss in 47 individuals from 28 (26 unrelated) families. In addition, 25/47 affected individuals (53%) presented with microcephaly, developmental delay/intellectual disability, cerebral palsy, and/or epilepsy. Modeling indicated damaging effect of variants on the protein, largely via destabilizing effects on protein domains. Brain imaging revealed diminished cerebral volume, thin corpus callosum, and periventricular leukomalacia, and quantitative volumetry demonstrated significantly diminished white matter volumes in several individuals. Immunofluorescent imaging in rat hippocampal neurons revealed localization of Spata5l1 in neuronal and glial cell nuclei and more prominent expression in neurons. In the rodent inner ear, Spata5l1 is expressed in the neurosensory hair cells and inner ear supporting cells. Transcriptomic analysis performed with fibroblasts from affected individuals was able to distinguish affected from controls by principal components. Analysis of differentially expressed genes and networks suggested a role for SPATA5L1 in cell surface adhesion receptor function, intracellular focal adhesions, and DNA replication and mitosis. Collectively, our results indicate that bi-allelic SPATA5L1 variants lead to a human disease characterized by sensorineural hearing loss (SNHL) with or without a nonprogressive mixed neurodevelopmental phenotype.

Grosch S, Kehrer M, Riess O, Bevot A, Haack TB. A further case of AFG2B-related neurodevelopmental disorder with hearing loss and microcephaly allows further clarification of pathogenicity of the variant c.1313T>C, p.(Leu438Pro). Mol Genet Genomic Med. 2024 Jan;12(1):e2310. doi: 10.1002/mgg3.2310. Epub 2023 Oct 30. PMID: 37902276; PMCID: PMC10767672.


Background: Bi-allelic variants in AFG2B (previously known as SPATA5L1) have recently been associated with a neurodevelopmental disorder with hearing loss and spasticity, as well as isolated hearing loss. We report on a 6 1/2-year-old girl with a history of global developmental delay, subsequent intellectual disability without relevant language acquisition, sensorineural hearing loss, muscular hypotonia and microcephaly.

Methods: We performed trio exome sequencing on the patient and her parents.

Results: Trio exome sequencing revealed likely pathogenic compound heterozygous missense variants in AFG2B [c.527G>T, p.(Gly176Val) and c.1313T>C, p.(Leu438Pro)] in the patient.

Conclusion: Of note, the change c.1313T>C, p.(Leu438Pro) has been observed in a previously published patient as part of a complex disease allele along with a second homozygous missense change, so the exact contribution of the two alterations to this patient's disease had initially remained unclear. Our results support the pathogenic relevance of the c.1313T>C, p.(Leu438Pro) allele while providing detailed insights into the disease manifestation of a further patient.

Keywords: AFG2B; neurodevelopmental disorder; trio exome sequencing.

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