SPATCCM

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SPATCCM
Symptoms microcephaly and significant developmental delay
Causes mutations in the SLC1A4 gene
Treatmentanti-epileptics

Spastic tetraplegia, thin corpus callosum, and progressive microcephaly (often referred to by its acronym SPATCCM) is a rare autosomal recessive disease caused by mutations in the SLC1A4 gene encoding the ASCT1 protein. The ASCT1 protein is primarily found in astrocytes in the brain where its main role is to import L-serine, a non-essential amino acid.

Contents

Symptoms and signs

Clinically, patients present with microcephaly and significant developmental delay. While some patients may be able to walk, others may not due to spasticity of limbs and hypotonic muscle tone, with progressive degeneration over time. Patients may also present with seizures, ranging from single febrile seizure to intractable epilepsy. Following brain MRI, patients may present with thin corpus callosum, decreased myelination, and/or brain atrophy. [1] These symptoms mimic that of other L-serine deficiencies [2]

Cause

There have so far been several identified mutations in the SLC1A4 gene that are linked to SPATCCM, including several frameshift (L314Hfs*42, [1] N324Tfs*29 [3] ), nonsense (Y191*, [4] W453* [5] ), duplication (L86_M88dup [6] ), and missense mutations (E256K, [1] [7] R457W, [1] G374R, [8] G381R, [9] S181F [3] ). These mutations interrupt the transport of serine from astrocytes to neurones, and across the blood brain barrier [10]

L-serine is important in brain development as it is a vital component in protein synthesis, as well as being the precursor to several essential compounds, including phosphatidylserine, sphingomyelin, glycine, and D-serine. [2]

Diagnosis

Diagnosis of SPATCCM generally relies on whole exome sequencing and the identification of a mutation in the SLC1A4 gene, while also lacking any other potential pathogenic mutations. [1]

Treatment

SPATCCM is an incurable genetic disease, however patients are often treated with anti-epileptics including vigabatrin, topiramate or clobazam, to reduce associated seizures. [4] [8] Supplementation of L-serine has also been proposed as a treatment. [1] [7] and has shown effective in a knock-in mouse model of the disease if administered prenatal and early postnatal. [10]

Epidemiology

Although most of the reported cases of SPATCCM are in people of Ashkenazi Jewish ancestry, it has also been reported in Irish, Hispanic, South Asian, Italian, Czech, Palestinian, and Pakistani ethnicities. [3] [5]

SPATCCM has a carrier frequency of 0.7% in the Ashkenazi Jewish population. [1]

References

  1. 1 2 3 4 5 6 7 Damseh N, Simonin A, Jalas C, Picoraro JA, Shaag A, Cho MT, et al. (August 2015). "Mutations in SLC1A4, encoding the brain serine transporter, are associated with developmental delay, microcephaly and hypomyelination". Journal of Medical Genetics. 52 (8): 541–547. doi:10.1136/jmedgenet-2015-103104. PMID   26041762.
  2. 1 2 El-Hattab AW (July 2016). "Serine biosynthesis and transport defects". Molecular Genetics and Metabolism. 118 (3): 153–159. doi:10.1016/j.ymgme.2016.04.010. PMID   27161889.
  3. 1 2 3 Mohamed FE, Ghattas MA, Almansoori TM, Tabouni M, Baydoun I, Kizhakkedath P, et al. (2023-07-12). "Novel compound heterozygous variants (c.971delA/c.542C > T) in SLC1A4 causes spastic tetraplegia, thin corpus callosum, and progressive microcephaly: a case report and mutational analysis". Frontiers in Pediatrics. 11 1183574. doi: 10.3389/fped.2023.1183574 . PMC   10369183 . PMID   37502193.
  4. 1 2 Abdelrahman HA, Al-Shamsi A, John A, Ali BR, Al-Gazali L (2019-01-01). "A Novel SLC1A4 Mutation (p.Y191*) Causes Spastic Tetraplegia, Thin Corpus Callosum, and Progressive Microcephaly (SPATCCM) With Seizure Disorder". Child Neurology Open. 6 2329048X19880647. doi:10.1177/2329048X19880647. PMC   6852354 . PMID   31763347.
  5. 1 2 Conroy J, Allen NM, Gorman K, O'Halloran E, Shahwan A, Lynch B, et al. (August 2016). "Novel European SLC1A4 variant: infantile spasms and population ancestry analysis". Journal of Human Genetics. 61 (8): 761–764. doi:10.1038/jhg.2016.44. PMID   27193218.
  6. ↑ Pujol-Giménez J, Mirzaa G, Blue EE, Albano G, Miller DE, Allworth A, et al. (June 2023). "Dominant-negative variant in SLC1A4 causes an autosomal dominant epilepsy syndrome". Annals of Clinical and Translational Neurology. 10 (6): 1046–1053. doi:10.1002/acn3.51786. PMC   10270265 . PMID   37194416.
  7. 1 2 Srour M, Hamdan FF, Gan-Or Z, Labuda D, Nassif C, Oskoui M, et al. (July 2015). "A homozygous mutation in SLC1A4 in siblings with severe intellectual disability and microcephaly". Clinical Genetics. 88 (1): e1 –e4. doi:10.1111/cge.12605. PMID   25930971.
  8. 1 2 Sarigecili E, Bulut FD, Anlas O (July 2022). "A rare cause of microcephaly, thin corpus callosum and refractory epilepsy due to a novel SLC1A4 gene mutation". Clinical Neurology and Neurosurgery. 218 107283. doi:10.1016/j.clineuro.2022.107283. PMID   35605507.
  9. ↑ Pironti E, Salpietro V, Cucinotta F, Granata F, Mormina E, Efthymiou S, et al. (December 2018). "A novel SLC1A4 homozygous mutation causing congenital microcephaly, epileptic encephalopathy and spastic tetraparesis: a video-EEG and tractography - case study". Journal of Neurogenetics. 32 (4): 316–321. doi:10.1080/01677063.2018.1476510. PMID   29989513.
  10. 1 2 Odeh M, Sajrawi C, Majcher A, Zubedat S, Shaulov L, Radzishevsky A, et al. (April 2024). "A new type of blood-brain barrier aminoacidopathy underlies metabolic microcephaly associated with SLC1A4 mutations". Brain. 147 (11): 3874–3889. doi:10.1093/brain/awae134. PMC   11531853 . PMID   38662784.
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