Mutations in PYCR2, encoding pyrroline-5-carboxylate reductase 2, cause microcephaly and hypomyelination

Tojo Nakayama, Almundher Al-Maawali, Malak El-Quessny, Anna Rajab, Samir Khalil, Joan M. Stoler, Wen Hann Tan, Ramzi Nasir, Klaus Schmitz-Abe, R. Sean Hill, Jennifer N. Partlow, Muna Al-Saffar, Sarah Servattalab, Christopher M. Lacoursiere, Dimira E. Tambunan, Michael E. Coulter, Princess C. Elhosary, Grzegorz Gorski, A. James Barkovich, Kyriacos Markianos & 2 others Annapurna Poduri, Ganeshwaran H. Mochida

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Despite recent advances in understanding the genetic bases of microcephaly, a large number of cases of microcephaly remain unexplained, suggesting that many microcephaly syndromes and associated genes have yet to be identified. Here, we report mutations in PYCR2, which encodes an enzyme in the proline biosynthesis pathway, as the cause of a unique syndrome characterized by postnatal microcephaly, hypomyelination, and reduced cerebral white-matter volume. Linkage mapping and whole-exome sequencing identified homozygous mutations (c.355C>T [p.Arg119Cys] and c.751C>T [p.Arg251Cys]) in PYCR2 in the affected individuals of two consanguineous families. A lymphoblastoid cell line from one affected individual showed a strong reduction in the amount of PYCR2. When mutant cDNAs were transfected into HEK293FT cells, both variant proteins retained normal mitochondrial localization but had lower amounts than the wild-type protein, suggesting that the variant proteins were less stable. A PYCR2-deficient HEK293FT cell line generated by genome editing with the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 system showed that PYCR2 loss of function led to decreased mitochondrial membrane potential and increased susceptibility to apoptosis under oxidative stress. Morpholino-based knockdown of a zebrafish PYCR2 ortholog, pycr1b, recapitulated the human microcephaly phenotype, which was rescued by wild-type human PYCR2 mRNA, but not by mutant mRNAs, further supporting the pathogenicity of the identified variants. Hypomyelination and the absence of lax, wrinkly skin distinguishes this condition from that caused by previously reported mutations in the gene encoding PYCR2's isozyme, PYCR1, suggesting a unique and indispensable role for PYCR2 in the human CNS during development.

Original languageEnglish
Pages (from-to)709-719
Number of pages11
JournalAmerican Journal of Human Genetics
Volume96
Issue number5
DOIs
Publication statusPublished - May 7 2015

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Pyrroline Carboxylate Reductases
Microcephaly
Mutation
Clustered Regularly Interspaced Short Palindromic Repeats
Exome
Cell Line
Morpholinos
Messenger RNA
Proteins
Mitochondrial Membrane Potential
Chromosome Mapping
Zebrafish
Proline
Isoenzymes
Genes
Virulence
Oxidative Stress
Complementary DNA
delta-1-pyrroline-5-carboxylate
Apoptosis

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

Cite this

Mutations in PYCR2, encoding pyrroline-5-carboxylate reductase 2, cause microcephaly and hypomyelination. / Nakayama, Tojo; Al-Maawali, Almundher; El-Quessny, Malak; Rajab, Anna; Khalil, Samir; Stoler, Joan M.; Tan, Wen Hann; Nasir, Ramzi; Schmitz-Abe, Klaus; Hill, R. Sean; Partlow, Jennifer N.; Al-Saffar, Muna; Servattalab, Sarah; Lacoursiere, Christopher M.; Tambunan, Dimira E.; Coulter, Michael E.; Elhosary, Princess C.; Gorski, Grzegorz; Barkovich, A. James; Markianos, Kyriacos; Poduri, Annapurna; Mochida, Ganeshwaran H.

In: American Journal of Human Genetics, Vol. 96, No. 5, 07.05.2015, p. 709-719.

Research output: Contribution to journalArticle

Nakayama, T, Al-Maawali, A, El-Quessny, M, Rajab, A, Khalil, S, Stoler, JM, Tan, WH, Nasir, R, Schmitz-Abe, K, Hill, RS, Partlow, JN, Al-Saffar, M, Servattalab, S, Lacoursiere, CM, Tambunan, DE, Coulter, ME, Elhosary, PC, Gorski, G, Barkovich, AJ, Markianos, K, Poduri, A & Mochida, GH 2015, 'Mutations in PYCR2, encoding pyrroline-5-carboxylate reductase 2, cause microcephaly and hypomyelination', American Journal of Human Genetics, vol. 96, no. 5, pp. 709-719. https://doi.org/10.1016/j.ajhg.2015.03.003
Nakayama, Tojo ; Al-Maawali, Almundher ; El-Quessny, Malak ; Rajab, Anna ; Khalil, Samir ; Stoler, Joan M. ; Tan, Wen Hann ; Nasir, Ramzi ; Schmitz-Abe, Klaus ; Hill, R. Sean ; Partlow, Jennifer N. ; Al-Saffar, Muna ; Servattalab, Sarah ; Lacoursiere, Christopher M. ; Tambunan, Dimira E. ; Coulter, Michael E. ; Elhosary, Princess C. ; Gorski, Grzegorz ; Barkovich, A. James ; Markianos, Kyriacos ; Poduri, Annapurna ; Mochida, Ganeshwaran H. / Mutations in PYCR2, encoding pyrroline-5-carboxylate reductase 2, cause microcephaly and hypomyelination. In: American Journal of Human Genetics. 2015 ; Vol. 96, No. 5. pp. 709-719.
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AU - Nakayama, Tojo

AU - Al-Maawali, Almundher

AU - El-Quessny, Malak

AU - Rajab, Anna

AU - Khalil, Samir

AU - Stoler, Joan M.

AU - Tan, Wen Hann

AU - Nasir, Ramzi

AU - Schmitz-Abe, Klaus

AU - Hill, R. Sean

AU - Partlow, Jennifer N.

AU - Al-Saffar, Muna

AU - Servattalab, Sarah

AU - Lacoursiere, Christopher M.

AU - Tambunan, Dimira E.

AU - Coulter, Michael E.

AU - Elhosary, Princess C.

AU - Gorski, Grzegorz

AU - Barkovich, A. James

AU - Markianos, Kyriacos

AU - Poduri, Annapurna

AU - Mochida, Ganeshwaran H.

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