#620393
Table of Contents
A number sign (#) is used with this entry because of evidence that autosomal recessive intellectual developmental disorder-79 (MRT79) is caused by compound heterozygous mutation in the TPR gene (189940) on chromosome 1q31. One such family has been reported.
Autosomal recessive intellectual developmental disorder-79 (MRT79) is characterized by global developmental delay apparent from infancy. Affected individuals have mildly delayed walking with an ataxic gait and severely impaired intellectual development with poor or absent speech. Additional features may include postnatal microcephaly and dysmorphic features (Van Bergen et al., 2022).
Van Bergen et al. (2022) reported 2 sibs, born of unrelated Maltese parents, with severely impaired intellectual development. The sister and brother, aged 21 and 16 years, respectively, showed global developmental delay from infancy, with walking between 25 and 27 months of age and severe language delay with absent speech beyond vocalization or a few words. The sister had mild hypotonia in the neonatal period and experienced episodes of stiffening and jerky movements in the first year of life; EEG was normal. Both sibs showed postnatal microcephaly, with head circumference falling below the first percentile. The patients were dependent for tasks of daily living. Physical examination showed an ataxic wide-based gait, dry eczematous skin, and dysmorphic features, including deep-set eyes, pseudostrabismus, prominent and broad nasal bridge, bulbous nasal tip, thin upper vermilion border, long and thin fingers, fifth finger clinodactyly, and hyperextensible joints. The sister showed head nod, intention tremor, and hand-flapping behaviors, and the brother had hand twirling. Brain imaging in the sister showed nonprogressive white matter changes and delayed myelination, whereas imaging in the brother showed prominent optic sheaths and thinning of the optic nerves.
The transmission pattern of MRT79 in the family reported by Van Bergen et al. (2022) was consistent with autosomal recessive inheritance.
In 2 sibs, born of unrelated Maltese parents, with MRT79, Van Bergen et al. (2022) identified compound heterozygous mutations in the TPR gene: a nonsense mutation (R2209X; 189940.0001) and a splice site mutation (189940.0002). The mutations, which were found by whole-genome sequencing, were each inherited from the unaffected parents; both mutations were absent from the gnomAD database. The findings were consistent with a loss-of-function effect, but the authors suggested that some residual function conferred by the splice site mutation may still exist. Patient fibroblasts showed decreased expression of the TPR protein and decreased density of TPR-containing nuclear pores in the nuclear envelope. The total intensity of mRNA in the nucleus was significantly reduced compared to controls, although cytoplasmic mRNA levels were unchanged. The findings suggested that depletion of TPR may cause defects in transcription with downstream effects on mRNA export.
Van Bergen, N. J., Bell, K. M., Carey, K., Gear, R., Massey, S., Murrell, E. K., Gallacher, L., Pope, K., Lockhart, P. J., Kornberg, A., Pais, L., Walkiewicz, M., Simons, C., MCRI Rare Diseases Flagship, Wickramasinghe, V. O., White, S. M., Christodoulou, J. Pathogenic variants in nucleoporin TPR (translocated promoter region, nuclear basket protein) cause severe intellectual disability in humans. Hum. Molec. Genet. 31: 362-375, 2022. [PubMed: 34494102, images, related citations] [Full Text]
Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
Gene/Locus |
Gene/Locus MIM number |
---|---|---|---|---|---|---|
1q31.1 | ?Intellectual developmental disorder, autosomal recessive 79 | 620393 | Autosomal recessive | 3 | TPR | 189940 |
A number sign (#) is used with this entry because of evidence that autosomal recessive intellectual developmental disorder-79 (MRT79) is caused by compound heterozygous mutation in the TPR gene (189940) on chromosome 1q31. One such family has been reported.
Autosomal recessive intellectual developmental disorder-79 (MRT79) is characterized by global developmental delay apparent from infancy. Affected individuals have mildly delayed walking with an ataxic gait and severely impaired intellectual development with poor or absent speech. Additional features may include postnatal microcephaly and dysmorphic features (Van Bergen et al., 2022).
Van Bergen et al. (2022) reported 2 sibs, born of unrelated Maltese parents, with severely impaired intellectual development. The sister and brother, aged 21 and 16 years, respectively, showed global developmental delay from infancy, with walking between 25 and 27 months of age and severe language delay with absent speech beyond vocalization or a few words. The sister had mild hypotonia in the neonatal period and experienced episodes of stiffening and jerky movements in the first year of life; EEG was normal. Both sibs showed postnatal microcephaly, with head circumference falling below the first percentile. The patients were dependent for tasks of daily living. Physical examination showed an ataxic wide-based gait, dry eczematous skin, and dysmorphic features, including deep-set eyes, pseudostrabismus, prominent and broad nasal bridge, bulbous nasal tip, thin upper vermilion border, long and thin fingers, fifth finger clinodactyly, and hyperextensible joints. The sister showed head nod, intention tremor, and hand-flapping behaviors, and the brother had hand twirling. Brain imaging in the sister showed nonprogressive white matter changes and delayed myelination, whereas imaging in the brother showed prominent optic sheaths and thinning of the optic nerves.
The transmission pattern of MRT79 in the family reported by Van Bergen et al. (2022) was consistent with autosomal recessive inheritance.
In 2 sibs, born of unrelated Maltese parents, with MRT79, Van Bergen et al. (2022) identified compound heterozygous mutations in the TPR gene: a nonsense mutation (R2209X; 189940.0001) and a splice site mutation (189940.0002). The mutations, which were found by whole-genome sequencing, were each inherited from the unaffected parents; both mutations were absent from the gnomAD database. The findings were consistent with a loss-of-function effect, but the authors suggested that some residual function conferred by the splice site mutation may still exist. Patient fibroblasts showed decreased expression of the TPR protein and decreased density of TPR-containing nuclear pores in the nuclear envelope. The total intensity of mRNA in the nucleus was significantly reduced compared to controls, although cytoplasmic mRNA levels were unchanged. The findings suggested that depletion of TPR may cause defects in transcription with downstream effects on mRNA export.
Van Bergen, N. J., Bell, K. M., Carey, K., Gear, R., Massey, S., Murrell, E. K., Gallacher, L., Pope, K., Lockhart, P. J., Kornberg, A., Pais, L., Walkiewicz, M., Simons, C., MCRI Rare Diseases Flagship, Wickramasinghe, V. O., White, S. M., Christodoulou, J. Pathogenic variants in nucleoporin TPR (translocated promoter region, nuclear basket protein) cause severe intellectual disability in humans. Hum. Molec. Genet. 31: 362-375, 2022. [PubMed: 34494102] [Full Text: https://doi.org/10.1093/hmg/ddab248]
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