Histone demethylase PHF8 promotes prostate cancer metastasis via the E2F1-SNAI1 axis.

Metastasis is the primary culprit behind cancer-related fatalities in multiple cancer types, including prostate cancer. Despite great advances, the precise mechanisms underlying prostate cancer metastasis are far from complete. By using a transgenic mouse prostate cancer model (TRAMP) with and without Phf8 knockout, we have identified a crucial role of PHF8 in prostate cancer metastasis. By complexing with E2F1, PHF8 transcriptionally upregulates SNAI1 in a demethylation-dependent manner. The upregulated SNAI1 subsequently enhances epithelial-to-mesenchymal transition (EMT) and metastasis. Given the role of the abnormally activated PHF8/E2F1-SNAI1 axis in prostate cancer metastasis and poor prognosis, the levels of PHF8 or the activity of this axis could serve as biomarkers for prostate cancer metastasis. Moreover, targeting this axis could become a potential therapeutic strategy for prostate cancer treatment. © 2024 The Pathological Society of Great Britain and Ireland.

A non-canonical role of ELN protects from cellular senescence by limiting iron-dependent regulation of gene expression.

The ELN gene encodes tropoelastin which is used to generate elastic fibers that insure proper tissue elasticity. Decreased amounts of elastic fibers and/or accumulation of bioactive products of their cleavage, named elastokines, are thought to contribute to aging. Cellular senescence, characterized by a stable proliferation arrest and by the senescence-associated secretory phenotype (SASP), increases with aging, fostering the onset and progression of age-related diseases and overall aging, and has so far never been linked with elastin. Here, we identified that decrease in ELN either by siRNA in normal human fibroblasts or by knockout in mouse embryonic fibroblasts results in premature senescence. Surprisingly this effect is independent of elastic fiber degradation or elastokines production, but it relies on the rapid increase in HMOX1 after ELN downregulation. Moreover, the induction of HMOX1 depends on p53 and NRF2 transcription factors, and leads to an increase in iron, further mediating ELN downregulation-induced senescence. Screening of iron-dependent DNA and histones demethylases revealed a role for histone PHF8 demethylase in mediating ELN downregulation-induced senescence. Collectively, these results unveil a role for ELN in protecting cells from cellular senescence through a non-canonical mechanism involving a ROS/HMOX1/iron accumulation/PHF8 histone demethylase pathway reprogramming gene expression towards a senescence program.

Role of plant homeodomain finger protein 8 in P19 embryonic carcinoma cells revealed by genome editing and specific inhibitor.

Plant homeodomain finger protein 8 (PHF8) is a histone demethylase that regulates the expression of various genes. PHF8 targets repressor histone markers and activates gene expression. Although PHF8 has been involved in X-linked mental retardation and certain types of cancers, the role of PHF8 remains largely unknown, and its relevance to the pathogenesis of these diseases is also uncertain. In the present study, we aimed to clarify the cellular function of PHF8 in P19 cells using Phf8 knockout (KO) cells generated via the CRISPR-Cas9 system and by performing PHF8 specific inhibitor experiments, instead of using PHF8 small interfering RNA transfection. After establishing Phf8 KO cells, we analyzed the effects of PHF8 on neuronal differentiation and cell proliferation. Both PHF8 deficiency and inhibition of its activity did not considerably affect neuronal differentiation, however, they showed an increased trend of promoted neurite outgrowth. Moreover, we found that PHF8 regulated cell proliferation via the MEK/ERK pathway. PHF8 deficiency and activity inhibition reduced the phosphorylation of ERK and MEK. The MEK expression level was associated with PHF8 expression, as revealed by chromatin immunoprecipitation analysis. These results suggested that PHF8 regulates cell proliferation via the MEK/ERK pathway in P19 embryonic carcinoma cells.

LncSUMO1P3 exacerbates malignant behaviors of esophageal squamous cell carcinoma cells via miR-486-5p/PHF8/CD151.

Background: Esophageal squamous cell carcinoma (ESCC) is a malignancy usually associated with smoking or alcohol consumption. The involvement of long noncoding RNAs (lncRNAs) in the regulation of tumor development and metastasis through molecular mechanisms has been unveiled by accumulating evidence. However, the function of lncRNA SUMO1 Pseudogene 3 (lncSUMO1P3) essential to ESCC development remains obscure. Methods: Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) and Western blot (WB) analysis were done to measure RNA and protein levels. Functional assays were carried out to examine the changes in ESCC cell phenotype. Supported by bioinformatics analysis, mechanism assays were done for assessment of putative interactions among different genes. Results: LlncSUMO1P3 was aberrantly up-regulated in ESCC cell lines, and lncSUMO1P3 deficiency could hamper cell proliferation, migration and invasion as well as epithelial-mesenchymaltransition (EMT) in ESCC while lncSUMO1P3 overexpression led to the opposite consequences. LncSUMO1P3 could competitively bind to microRNA-486-5p (miR-486-5p) or PHD finger protein 8 (PHF8) to modulate CD151 expression. CD151 was also verified to regulate ESCC cell biological behaviors. Conclusion: Our study revealed that lncSUMO1P3, up-regulated in ESCC cells, could sponge miR-486-5p and recruit PHF8 to up-regulate CD151, thus influencing the malignant behaviors of ESCC cells.

Deletion of the Homocysteine Thiolactone Detoxifying Enzyme Bleomycin Hydrolase, in Mice, Causes Memory and Neurological Deficits and Worsens Alzheimer's Disease-Related Behavioral and Biochemical Traits in the 5xFAD Model of Alzheimer's Disease.

BACKGROUND: Bleomycin hydrolase (BLMH), a homocysteine (Hcy)-thiolactone detoxifying enzyme, is attenuated in Alzheimer's disease (AD) brains. Blmh loss causes astrogliosis in mice while the loss of histone demethylase Phf8, which controls mTOR signaling, causes neuropathy in mice and humans. OBJECTIVE: To examine how Blmh gene deletion affects the Phf8/H4K20me1/mTOR/autophagy pathway, amyloid-ß (Aß) accumulation, and cognitive/neuromotor performance in mice. METHODS: We generated a new mouse model of AD, the Blmh-/-5xFAD mouse. Behavioral assessments were conducted by cognitive/neuromotor testing. Blmh and Phf8 genes were silenced in mouse neuroblastoma N2a-APPswe cells by RNA interference. mTOR- and autophagy-related proteins, and AßPP were quantified by western blotting and the corresponding mRNAs by RT-qPCR. Aß was quantified by western blotting (brains) and by confocal microscopy (cells). RESULTS: Behavioral testing showed cognitive/neuromotor deficits in Blmh-/- and Blmh-/-5xFAD mice. Phf8 was transcriptionally downregulated in Blmh-/- and Blmh-/-5xFAD brains. H4K20me1, mTOR, phospho-mTOR, and AßPP were upregulated while autophagy markers Becn1, Atg5, and Atg7 were downregulated in Blmh-/- and Blmh-/-5xFAD brains. Aß was elevated in Blmh-/-5xFAD brains. These biochemical changes were recapitulated in Blmh-silenced N2a-APPswe cells, which also showed increased H4K20me1-mTOR promoter binding and impaired autophagy flux (Lc3-I, Lc3-II, p62). Phf8-silencing or treatments with Hcy-thiolactone or N-Hcy-protein, metabolites elevated in Blmh-/- mice, induced biochemical changes in N2a-APPswe cells like those induced by the Blmh-silencing. However, Phf8-silencing elevated Aß without affecting AßPP. CONCLUSIONS: Our findings show that Blmh interacts with AßPP and the Phf8/H4K20me1/mTOR/autophagy pathway, and that disruption of those interactions causes Aß accumulation and cognitive/neuromotor deficits.

KDM7 Demethylases: Regulation, Function and Therapeutic Targeting.

It was more than a decade ago that PHF8, KDM7A/JHDM1D and PHF2 were first proposed to be a histone demethylase family and were named as KDM7 (lysine demethylase) family. Since then, knowledge of their demethylation activities, roles as co-regulators of transcription and roles in development and diseases such as cancer has been steadily growing. The demethylation activities of PHF8 and KDM7A toward various methylated histones including H3K9me2/1, H3K27me2 and H4K20me1 have been identified and proven in various cell types. In contrast, PHF2, due to a mutation of a key residue in an iron-binding domain, demethylates H3K9me2 upon PKA-mediated phosphorylation. Interestingly, it was reported that PHF2 possesses an unusual H4K20me3 demethylation activity, which was not observed for PHF8 and KDM7A. PHF8 has been most extensively studied with respect to its roles in development and oncogenesis, revealing that it contributes to regulation of the cell cycle, cell viability and cell migration. Moreover, accumulating lines of evidence demonstrated that the KDM7 family members are subjected to post-transcriptional and post-translational regulations, leading to a higher horizon for evaluating their actual protein expression and functions in development and cancer. This chapter provides a general view of the current understanding of the regulation and functions of the KDM7 family and discusses their potential as therapeutic targets in cancer as well as perspectives for further studies.

Histone demethylase PHF8 facilitates the development of chronic myeloid leukaemia by directly targeting BCR::ABL1.

Although tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukaemia (CML), TKI resistance remains a major challenge. Here, we demonstrated that plant homeodomain finger protein 8 (PHF8), a histone demethylase was aberrantly enriched in CML samples compared to healthy controls. PHF8 inhibited CML cell differentiation and promoted CML cell proliferation. Furthermore, the proliferation-inhibited function of PHF8-knockdown have stronger effect on imatinib mesylate (IM)-resistant CML cells. Mechanistically, we identified that PHF8 as a transcriptional modulator interacted with the promoter of the BCR::ABL1 fusion gene and alters the methylation levels of H3K9me1, H3K9me2 and H3K27me1, thereby promoting BCR::ABL1 transcription. Overall, our study suggests that targeting PHF8, which directly regulates BCR::ABL1 expression, is a useful therapeutic approach for CML.

Homocysteine metabolites inhibit autophagy, elevate amyloid beta, and induce neuropathy by impairing Phf8/H4K20me1-dependent epigenetic regulation of mTOR in cystathionine ß-synthase-deficient mice.

The loss of cystathionine ß-synthase (CBS), an important homocysteine (Hcy)-metabolizing enzyme or the loss of PHF8, an important histone demethylase participating in epigenetic regulation, causes severe intellectual disability in humans. Similar neuropathies were also observed in Cbs-/- and Phf8-/- mice. How CBS or PHF8 depletion can cause neuropathy was unknown. To answer this question, we examined a possible interaction between PHF8 and CBS using Cbs-/- mouse and neuroblastoma cell models. We quantified gene expression by RT-qPCR and western blotting, mTOR-bound H4K20me1 by chromatin immunoprecipitation (CHIP) assay, and amyloid ß (Aß) by confocal fluorescence microscopy using anti-Aß antibody. We found significantly reduced expression of Phf8, increased H4K20me1, increased mTOR expression and phosphorylation, and increased App, both on protein and mRNA levels in brains of Cbs-/- mice versus Cbs+/- sibling controls. Autophagy-related Becn1, Atg5, and Atg7 were downregulated while p62, Nfl, and Gfap were upregulated on protein and mRNA levels, suggesting reduced autophagy and increased neurodegeneration in Cbs-/- brains. In mouse neuroblastoma N2a or N2a-APPswe cells, treatments with Hcy-thiolactone, N-Hcy-protein or Hcy, or Cbs gene silencing by RNA interference significantly reduced Phf8 expression and increased total H4K20me1 as well as mTOR promoter-bound H4K20me1. This led to transcriptional mTOR upregulation, autophagy downregulation, and significantly increased APP and Aß levels. The Phf8 gene silencing increased Aß, but not APP, levels. Taken together, our findings identify Phf8 as a regulator of Aß synthesis and suggest that neuropathy of Cbs deficiency is mediated by Hcy metabolites, which transcriptionally dysregulate the Phf8 → H4K20me1 → mTOR → autophagy pathway thereby increasing Aß accumulation.

Expression Patterns of PAK4 and PHF8 Are Associated with the Survival of Gallbladder Carcinoma Patients.

BACKGROUND: PAK4 and PHF8 are involved in cancer progression and are under evaluation as targets for cancer therapy. However, despite extensive studies in human cancers, there are limited reports on the roles of PAK4 and PHF8 in gallbladder cancers. METHODS: Immunohistochemical expression of PAK4 and PHF8 and their prognostic significance were evaluated in 148 human gallbladder carcinomas. RESULTS: PAK4 expression was significantly associated with PHF8 expression in gallbladder carcinomas. Positive expression of nuclear PAK4, cytoplasmic PAK4, nuclear PHF8, and cytoplasmic PHF8 were significantly associated with shorter overall survival and relapse-free survival in univariate analysis. Multivariate analysis showed that nuclear PAK4 expression and nuclear PHF8 expression were independent predictors of overall survival and relapse-free survival in gallbladder carcinomas. Furthermore, coexpression of nuclear PAK4 and nuclear PHF8 predicted shorter overall survival (p < 0.001) and relapse-free survival (p < 0.001) of gallbladder carcinoma in multivariate analysis. CONCLUSIONS: This study suggests that the individual and coexpression patterns of PAK4 and PHF8 as the prognostic indicators for gallbladder carcinoma patients.

Depletion of Paraoxonase 1 (Pon1) Dysregulates mTOR, Autophagy, and Accelerates Amyloid Beta Accumulation in Mice.

Paraoxonase 1 (PON1), a homocysteine (Hcy)-thiolactone detoxifying enzyme, has been associated with Alzheimer's disease (AD), suggesting that PON1 plays an important protective role in the brain. To study the involvement of PON1 in the development of AD and to elucidate the mechanism involved, we generated a new mouse model of AD, the Pon1-/-xFAD mouse, and examined how Pon1 depletion affects mTOR signaling, autophagy, and amyloid beta (Aß) accumulation. To elucidate the mechanism involved, we examined these processes in N2a-APPswe cells. We found that Pon1 depletion significantly downregulated Phf8 and upregulated H4K20me1; mTOR, phospho-mTOR, and App were upregulated while autophagy markers Bcln1, Atg5, and Atg7 were downregulated at the protein and mRNA levels in the brains of Pon1─/─5xFAD vs. Pon1+/+5xFAD mice. Pon1 depletion in N2a-APPswe cells by RNA interference led to downregulation of Phf8 and upregulation of mTOR due to increased H4K20me1-mTOR promoter binding. This led to autophagy downregulation and significantly increased APP and Aß levels. Phf8 depletion by RNA interference or treatments with Hcy-thiolactone or N-Hcy-protein metabolites similarly increased Aß levels in N2a-APPswe cells. Taken together, our findings define a neuroprotective mechanism by which Pon1 prevents Aß generation.

A Proteome-Wide Effect of PHF8 Knockdown on Cortical Neurons Shows Downregulation of Parkinson's Disease-Associated Protein Alpha-Synuclein and Its Interactors.

Synaptic dysfunction may underlie the pathophysiology of Parkinson's disease (PD), a presently incurable condition characterized by motor and cognitive symptoms. Here, we used quantitative proteomics to study the role of PHD Finger Protein 8 (PHF8), a histone demethylating enzyme found to be mutated in X-linked intellectual disability and identified as a genetic marker of PD, in regulating the expression of PD-related synaptic plasticity proteins. Amongst the list of proteins found to be affected by PHF8 knockdown were Parkinson's-disease-associated SNCA (alpha synuclein) and PD-linked genes DNAJC6 (auxilin), SYNJ1 (synaptojanin 1), and the PD risk gene SH3GL2 (endophilin A1). Findings in this study show that depletion of PHF8 in cortical neurons affects the activity-induced expression of proteins involved in synaptic plasticity, synaptic structure, vesicular release and membrane trafficking, spanning the spectrum of pre-synaptic and post-synaptic transmission. Given that the depletion of even a single chromatin-modifying enzyme can affect synaptic protein expression in such a concerted manner, more in-depth studies will be needed to show whether such a mechanism can be exploited as a potential disease-modifying therapeutic drug target in PD.

Oncogenic lncRNA BBOX1-AS1 promotes PHF8-mediated autophagy and elicits sorafenib resistance in hepatocellular carcinoma.

Some long non-coding RNAs (lncRNAs) have been documented to be involved in cancer progression and anticancer drug resistance in hepatocellular carcinoma (HCC). Thus, approaches designed to target these genes may facilitate the development of promising strategies for treating HCC. Previously, we showed that lncRNA BBOX1-AS1 was highly expressed and played an oncogenic role in HCC. However, the potential functions and mechanisms through which BBOX1-AS1 regulates HCC progression and drug resistance remain unclear. This study revealed that BBOX1-AS1 could promote tumor progression, autophagy, and drug resistance by upregulating PHF8 in HCC cells. Mechanistically, BBOX1-AS1 enhanced the stability of PHF8 mRNA by targeting the PHF8 inhibitor miR-361-3p to regulate tumor progression and autophagy in HCC. The functional rescue experiments showed that PHF8 acted as a key factor in regulating the biological effects induced by BBOX1-AS1 and miR-361-3p in HCC, indicating that BBOX1-AS1 promotes tumor progression and sorafenib resistance by regulating miR-361-3p/PHF8. Finally, mouse tumor models and patient-derived organoid models were established to further confirm these findings. Taken together, the results demonstrate that BBOX1-AS1 promotes HCC progression and sorafenib resistance via the miR-361-3p/PHF8 axis.

Functional Characterization of a Phf8 Processed Pseudogene in the Mouse Genome.

Most pseudogenes are generated when an RNA transcript is reverse-transcribed and integrated into the genome at a new location. Pseudogenes are often considered as an imperfect and silent copy of a functional gene because of the accumulation of numerous mutations in their sequence. Here we report the presence of Pfh8-ps, a Phf8 retrotransposed pseudogene in the mouse genome, which has no disruptions in its coding sequence. We show that this pseudogene is mainly transcribed in testis and can produce a PHF8-PS protein in vivo. As the PHF8-PS protein has a well-conserved JmjC domain, we characterized its enzymatic activity and show that PHF8-PS does not have the intrinsic capability to demethylate H3K9me2 in vitro compared to the parental PHF8 protein. Surprisingly, PHF8-PS does not localize in the nucleus like PHF8, but rather is mostly located at the cytoplasm. Finally, our proteomic analysis of PHF8-PS-associated proteins revealed that PHF8-PS interacts not only with mitochondrial proteins, but also with prefoldin subunits (PFDN proteins) that deliver unfolded proteins to the cytosolic chaperonin complex implicated in the folding of cytosolic proteins. Together, our findings highlighted PHF8-PS as a new pseudogene-derived protein with distinct molecular functions from PHF8.

NEDD4L represses prostate cancer cell proliferation via modulating PHF8 through the ubiquitin–proteasome pathway

Purpose Prostate cancer (PC) is a heterogeneous malignancy that greatly threatens man’s health. E3 ubiquitin-protein ligase neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) imparts an regulatory role in various malignancies. This study focused on the modulatory mechanism of NEDD4L in proliferation of prostate cancer cells (PCCs) via regulating histone demethylase plant homeodomain finger protein 8 (PHF8/KDM7B) through the ubiquitin–proteasome system. Methods The expression levels of NEDD4L, PHF8, H3 lysine 9 dimethylation (H3K9me2) and activating transcription factor 2 (ATF2) in PC tissues and cell lines were detected via real-time quantitative polymerase chain reaction and Western blotting. After transfection of pcDNA3.1-NEDD4L, pcDNA3.1-PHF8, and pcDNA3.1-ATF2 into PCCs, cell proliferation was assessed via the cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays. Interaction between NEDD4L and PHF8 was identified via the protein immunoprecipitation. The ubiquitination level of PHF8 was determined via the ubiquitination detection. The enrichments of H3K9me2 and PHF8 in the ATF2 promotor region were detected via the chromatin-immunoprecipitation assay. Results PHF8 and ATF2 were highly expressed while NEDD4L was poorly expressed in PC tissues and cells. NEDD4L overexpression reduced proliferation of PCCs. NEDD4L induced degradation of PHF8 via ubiquitination. PHF8 limited the enrichment of H3K9me2 in the ATF2 promotor region and enhanced ATF2 transcription. Up regulation of PHF8 or ATF2 abolished the inhibitory role of NEDD4L in proliferation of PCCs. Conclusion NEDD4L facilitated degradation of PHF8 to limit ATF2 transcription, thereby suppressing proliferation of PCCs. (AU)

NEDD4L represses prostate cancer cell proliferation via modulating PHF8 through the ubiquitin-proteasome pathway.

PURPOSE: Prostate cancer (PC) is a heterogeneous malignancy that greatly threatens man's health. E3 ubiquitin-protein ligase neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) imparts an regulatory role in various malignancies. This study focused on the modulatory mechanism of NEDD4L in proliferation of prostate cancer cells (PCCs) via regulating histone demethylase plant homeodomain finger protein 8 (PHF8/KDM7B) through the ubiquitin-proteasome system. METHODS: The expression levels of NEDD4L, PHF8, H3 lysine 9 dimethylation (H3K9me2) and activating transcription factor 2 (ATF2) in PC tissues and cell lines were detected via real-time quantitative polymerase chain reaction and Western blotting. After transfection of pcDNA3.1-NEDD4L, pcDNA3.1-PHF8, and pcDNA3.1-ATF2 into PCCs, cell proliferation was assessed via the cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays. Interaction between NEDD4L and PHF8 was identified via the protein immunoprecipitation. The ubiquitination level of PHF8 was determined via the ubiquitination detection. The enrichments of H3K9me2 and PHF8 in the ATF2 promotor region were detected via the chromatin-immunoprecipitation assay. RESULTS: PHF8 and ATF2 were highly expressed while NEDD4L was poorly expressed in PC tissues and cells. NEDD4L overexpression reduced proliferation of PCCs. NEDD4Linduced degradation of PHF8 via ubiquitination. PHF8 limited the enrichment of H3K9me2 in the ATF2 promotor region and enhanced ATF2 transcription. Upregulation of PHF8 or ATF2 abolished the inhibitory role of NEDD4L in proliferation of PCCs. CONCLUSION: NEDD4L facilitated degradation of PHF8 to limit ATF2 transcription, thereby suppressing proliferation of PCCs.

PHF8 promotes osteogenic differentiation of BMSCs in old rat with osteoporosis by regulating Wnt/ß-catenin pathway.

Osteoporosis is a progressive bone disorder with a higher incidence in the elderly and has become a major public health concern all over the world. Therefore, it is urgent to investigate the mechanisms underlying the pathogenesis of osteoporosis. In this study, the osteoporosis animal model was established, and then rat bone marrow mesenchymal stem cells (rBMSCs) were cultured. The results showed that PHF8 expression was decreased in osteoporosis rats compared to controls. Overexpression of PHF8 promoted BMSC osteogenic differentiation and the expression of osteogenesis-related genes. In addition, the Wnt/ß-catenin signaling pathway in BMSCs was inhibited in osteoporosis rats, which was rescued by overexpression of PHF8. After treatment with the Wnt pathway antagonist, the improved osteogenic differentiation of BMSCs induced by overexpression of PHF8 was blocked. Collectively, our data revealed that the decreased expression of PHF8 in osteoporosis rats suppressed the osteogenic differentiation of BMSCs, which was then restored by PHF8 overexpression. Furthermore, the inhibition of the Wnt/ß-catenin signaling pathway in BMSCs suppressed osteogenic differentiation. Thus, these findings indicated that PHF8 plays a role in osteogenic differentiation through the Wnt/ß-catenin signaling pathway.

Variants in PHF8 cause a spectrum of X-linked neurodevelopmental disorders and facial dysmorphology.

Loss-of-function variants in PHD Finger Protein 8 (PHF8) cause Siderius X-linked intellectual disability (ID) syndrome, hereafter called PHF8-XLID. PHF8 is a histone demethylase that is important for epigenetic regulation of gene expression. PHF8-XLID is an under-characterized disorder with only five previous reports describing different PHF8 predicted loss-of-function variants in eight individuals. Features of PHF8-XLID include ID and craniofacial dysmorphology. In this report we present 16 additional individuals with PHF8-XLID from 11 different families of diverse ancestry. We also present five individuals from four different families who have ID and a variant of unknown significance in PHF8 with no other explanatory variant in another gene. All affected individuals exhibited developmental delay and all but two had borderline to severe ID. Of the two who did not have ID, one had dyscalculia and the other had mild learning difficulties. Craniofacial findings such as hypertelorism, microcephaly, elongated face, ptosis, and mild facial asymmetry were found in some affected individuals. Orofacial clefting was seen in three individuals from our cohort, suggesting that this feature is less common than previously reported. Autism spectrum disorder and attention deficit hyperactivity disorder, which were not previously emphasized in PHF8-XLID, were frequently observed in affected individuals. This series expands the clinical phenotype of this rare ID syndrome caused by loss of PHF8 function.

The histone demethylase PHF8 regulates astrocyte differentiation and function.

Epigenetic factors have been shown to play a crucial role in X-linked intellectual disability (XLID). Here, we investigate the contribution of the XLID-associated histone demethylase PHF8 to astrocyte differentiation and function. Using genome-wide analyses and biochemical assays in mouse astrocytic cultures, we reveal a regulatory crosstalk between PHF8 and the Notch signaling pathway that balances the expression of the master astrocytic gene Nfia. Moreover, PHF8 regulates key synaptic genes in astrocytes by maintaining low levels of H4K20me3. Accordingly, astrocytic-PHF8 depletion has a striking effect on neuronal synapse formation and maturation in vitro. These data reveal that PHF8 is crucial in astrocyte development to maintain chromatin homeostasis and limit heterochromatin formation at synaptogenic genes. Our studies provide insights into the involvement of epigenetics in intellectual disability.

Histone demethylase PHF8 drives neuroendocrine prostate cancer progression by epigenetically upregulating FOXA2.

Neuroendocrine prostate cancer (NEPC) is a more aggressive subtype of castration-resistant prostate cancer (CRPC). Although it is well established that PHF8 can enhance prostate cancer cell proliferation, whether PHF8 is involved in prostate cancer initiation and progression is relatively unclear. By comparing the transgenic adenocarcinoma of the mouse prostate (TRAMP) mice with or without Phf8 knockout, we systemically examined the role of PHF8 in prostate cancer development. We found that PHF8 plays a minimum role in initiation and progression of adenocarcinoma. However, PHF8 is essential for NEPC because not only is PHF8 highly expressed in NEPC but also animals without Phf8 failed to develop NEPC. Mechanistically, PHF8 transcriptionally upregulates FOXA2 by demethylating and removing the repressive histone markers on the promoter region of the FOXA2 gene, and the upregulated FOXA2 subsequently regulates the expression of genes involved in NEPC development. Since both PHF8 and FOXA2 are highly expressed in NEPC tissues from patients or patient-derived xenografts, the levels of PHF8 and FOXA2 can either individually or in combination serve as NEPC biomarkers and targeting either PHF8 or FOXA2 could be potential therapeutic strategies for NEPC treatment. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Histone Demethylase PHF8 Is Required for the Development of the Zebrafish Inner Ear and Posterior Lateral Line.

Histone demethylase PHF8 is crucial for multiple developmental processes, and hence, the awareness of its function in developing auditory organs needs to be increased. Using in situ hybridization (ISH) labeling, the mRNA expression of PHF8 in the zebrafish lateral line system and otic vesicle was monitored. The knockdown of PHF8 by morpholino significantly disrupted the development of the posterior lateral line system, which impacted cell migration and decreased the number of lateral line neuromasts. The knockdown of PHF8 also resulted in severe malformation of the semicircular canal and otoliths in terms of size, quantity, and position during the inner ear development. The loss of function of PHF8 also induced a defective differentiation in sensory hair cells in both lateral line neuromasts and the inner ear. ISH analysis of embryos that lacked PHF8 showed alterations in the expression of many target genes of several signaling pathways concerning cell migration and deposition, including the Wnt and FGF pathways. In summary, the current findings established PHF8 as a novel epigenetic element in developing auditory organs, rendering it a potential candidate for hearing loss therapy.