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Impaired protein hydroxylase activity causes replication stress and developmental abnormalities in humans
Sally C. Fletcher, Charlotte Hall, Tristan J. Kennedy, Sander Pajusalu, Monica H. Wojcik, Uncaar Boora, Chan Li, Kaisa Teele Oja, Eline Hendrix, Christian A.E. Westrip, Regina Andrijes, Sonia K. Piasecka, Mansi Singh, Mohammed E. El-Asrag, Anetta Ptasinska, Vallo Tillmann, Martin R. Higgs, Deanna A. Carere, Andrew D. Beggs, John Pappas, Rachel Rabin, Stephen J. Smerdon, Grant S. Stewart, Katrin Õunap, Mathew L. Coleman
Sally C. Fletcher, Charlotte Hall, Tristan J. Kennedy, Sander Pajusalu, Monica H. Wojcik, Uncaar Boora, Chan Li, Kaisa Teele Oja, Eline Hendrix, Christian A.E. Westrip, Regina Andrijes, Sonia K. Piasecka, Mansi Singh, Mohammed E. El-Asrag, Anetta Ptasinska, Vallo Tillmann, Martin R. Higgs, Deanna A. Carere, Andrew D. Beggs, John Pappas, Rachel Rabin, Stephen J. Smerdon, Grant S. Stewart, Katrin Õunap, Mathew L. Coleman
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Research Article Cell biology Genetics

Impaired protein hydroxylase activity causes replication stress and developmental abnormalities in humans

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Abstract

Although protein hydroxylation is a relatively poorly characterized posttranslational modification, it has received significant recent attention following seminal work uncovering its role in oxygen sensing and hypoxia biology. Although the fundamental importance of protein hydroxylases in biology is becoming clear, the biochemical targets and cellular functions often remain enigmatic. JMJD5 is a “JmjC-only” protein hydroxylase that is essential for murine embryonic development and viability. However, no germline variants in JmjC-only hydroxylases, including JMJD5, have yet been described that are associated with any human pathology. Here we demonstrate that biallelic germline JMJD5 pathogenic variants are deleterious to JMJD5 mRNA splicing, protein stability, and hydroxylase activity, resulting in a human developmental disorder characterized by severe failure to thrive, intellectual disability, and facial dysmorphism. We show that the underlying cellular phenotype is associated with increased DNA replication stress and that this is critically dependent on the protein hydroxylase activity of JMJD5. This work contributes to our growing understanding of the role and importance of protein hydroxylases in human development and disease.

Authors

Sally C. Fletcher, Charlotte Hall, Tristan J. Kennedy, Sander Pajusalu, Monica H. Wojcik, Uncaar Boora, Chan Li, Kaisa Teele Oja, Eline Hendrix, Christian A.E. Westrip, Regina Andrijes, Sonia K. Piasecka, Mansi Singh, Mohammed E. El-Asrag, Anetta Ptasinska, Vallo Tillmann, Martin R. Higgs, Deanna A. Carere, Andrew D. Beggs, John Pappas, Rachel Rabin, Stephen J. Smerdon, Grant S. Stewart, Katrin Õunap, Mathew L. Coleman

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Figure 4

Biallelic JMJD5 pathogenic variants are associated with increased markers of replication stress.

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Biallelic JMJD5 pathogenic variants are associated with increased marker...
Immortalized fibroblasts were monitored for 2 commonly used markers of replication stress (micronuclei and 53BP1 bodies). The affected Sib4In/CY fibroblasts show significantly increased replication stress. (A) 53BP1 bodies were counted using immunofluorescence staining and distinguished from 53BP1 foci based on their size and presence only in G1 cells (using costaining for CENPF). Shown are examples of cells with different numbers of 53BP1 bodies. (B) 53BP1 bodies in untreated cells were significantly increased in Sib4In/CY immortalized fibroblasts. APH indicates aphidicolin, a DNA polymerase inhibitor that is an established replication stress stimulus (see below). (C) 53BP1 bodies were also significantly increased in Sib4In/CY immortalized fibroblasts treated with APH (0.5 μM for 48 hours). (D) Micronuclei were counted following DAPI staining. Shown are 2 examples of cells with micronuclei. (E) Micronuclei were significantly increased in untreated Sib4In/CY immortalized fibroblasts. (F) Micronuclei were also significantly increased in Sib4In/CY immortalized fibroblasts treated with APH. (B, C, E, and F) Data represent mean ± SEM from 5 independent experiments. For 53BP1 bodies, a minimum of 300 cells were counted per sample. For micronuclei, a minimum of 500 cells were counted per sample. Statistical analyses used 1-way ANOVA with Tukey’s post hoc test; *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001.

Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)

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