PRKDC mutations in a SCID patient with profound neurological abnormalities
Lisa Woodbine, Jessica A. Neal, Nanda-Kumar Sasi, Mayuko Shimada, Karen Deem, Helen Coleman, William B. Dobyns, Tomoo Ogi, Katheryn Meek, E. Graham Davies, Penny A. Jeggo
Lisa Woodbine, Jessica A. Neal, Nanda-Kumar Sasi, Mayuko Shimada, Karen Deem, Helen Coleman, William B. Dobyns, Tomoo Ogi, Katheryn Meek, E. Graham Davies, Penny A. Jeggo
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Research Article Genetics

PRKDC mutations in a SCID patient with profound neurological abnormalities

Abstract

The DNA-dependent protein kinase catalytic subunit (DNA-PKcs; encoded by PRKDC) functions in DNA non-homologous end-joining (NHEJ), the major DNA double strand break (DSB) rejoining pathway. NHEJ also functions during lymphocyte development, joining V(D)J recombination intermediates during antigen receptor gene assembly. Here, we describe a patient with compound heterozygous mutations in PRKDC, low DNA-PKcs expression, barely detectable DNA-PK kinase activity, and impaired DSB repair. In a heterologous expression system, we found that one of the PRKDC mutations inactivated DNA-PKcs, while the other resulted in dramatically diminished but detectable residual function. The patient suffered SCID with reduced or absent T and B cells, as predicted from PRKDC-deficient animal models. Unexpectedly, the patient was also dysmorphic; showed severe growth failure, microcephaly, and seizures; and had profound, globally impaired neurological function. MRI scans revealed microcephaly-associated cortical and hippocampal dysplasia and progressive atrophy over 2 years of life. These neurological features were markedly more severe than those observed in patients with deficiencies in other NHEJ proteins. Although loss of DNA-PKcs in mice, dogs, and horses was previously shown not to impair neuronal development, our findings demonstrate a stringent requirement for DNA-PKcs during human neuronal development and suggest that high DNA-PK protein expression is required to sustain efficient pre- and postnatal neurogenesis.

Authors

Lisa Woodbine, Jessica A. Neal, Nanda-Kumar Sasi, Mayuko Shimada, Karen Deem, Helen Coleman, William B. Dobyns, Tomoo Ogi, Katheryn Meek, E. Graham Davies, Penny A. Jeggo

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Figure 4

Identification of mutational changes in PRKDC cDNA.

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Identification of mutational changes in PRKDC cDNA. (A) Dye-terminator...
(A) Dye-terminator sequence figures illustrating the c.10721C>T mutational change in 1 allele of the patient and mother. (B) Dye-terminator sequence figures illustrating a double sequence commencing at c.1624, the bp at the boundary between exons 15 and 16. (C) RT-PCR amplification products using primers located in exons 15 and 17. Control cells yielded a single product of the size anticipated for the presence of exon 16. Patient cells yielded 2 bands, the smaller of which was the size expected for a product lacking exon 16. The greater signal could be the result of enhanced amplification of a smaller fragment. (D) mRNA transcript levels, determined using primers specific for HPRT, the WT p.A3574 allele (PRKDC c.10712C), or the mutant p.A3574V allele (PRKDC c.10712C>T). All cell lines showed equal expression of HPRT. cDNA of 48BR control cells had 2-fold greater levels of the WT allele compared with cDNA from mother or patient cells, which expressed the same level of the p.A3574 and p.A3574V mutant alleles. (E) Conservation of the A3574 residue between species and location of the identified mutational changes in PRKDC in relation to important domains.