Single substitution in H3.3G34 alters DNMT3A recruitment to cause progressive neurodegeneration.

Germline histone H3.3 amino acid substitutions, including H3.3G34R/V, cause severe neurodevelopmental syndromes. To understand how these mutations impact brain development, we generated H3.3G34R/V/W knock-in mice and identified strikingly distinct developmental defects for each mutation. H3.3G34R-mutants exhibited progressive microcephaly and neurodegeneration, with abnormal accumulation of disease-associated microglia and concurrent neuronal depletion. G34R severely decreased H3K36me2 on the mutant H3.3 tail, impairing recruitment of DNA methyltransferase DNMT3A and its redistribution on chromatin. These changes were concurrent with sustained expression of complement and other innate immune genes possibly through loss of non-CG (CH) methylation and silencing of neuronal gene promoters through aberrant CG methylation. Complement expression in G34R brains may lead to neuroinflammation possibly accounting for progressive neurodegeneration. Our study reveals that H3.3G34-substitutions have differential impact on the epigenome, which underlie the diverse phenotypes observed, and uncovers potential roles for H3K36me2 and DNMT3A-dependent CH-methylation in modulating synaptic pruning and neuroinflammation in post-natal brains.

Whole-exome sequencing reveals novel vacuolar ATPase genes' variants and variants in genes involved in lysosomal biology and autophagosomal formation in oral granular cell tumors.

BACKGROUND: Granular cell tumors (GCTs) are rare neuroectodermal soft tissue neoplasms that mainly affect the skin of the upper limbs and trunks and the oral cavity. GCTs are derived from Schwann cells and, ultrastructurally, their intracytoplasmic granules are considered autophagosomes or autophagolysosomes and are consistent with myelin accumulation. METHODS: In this study, a convenience set of 22 formalin-fixed, paraffin-embedded samples of oral GCTs, all but one sample located at the tongue, was screened for mutations by whole-exome (WES) or targeted sequencing. RESULTS: WES revealed two novel variants in genes of the vacuolar ATPase (V-ATPase) complex: ATP6AP1 frameshift c.746_749del, leading to p.P249Hfs*4, and ATP6V1A non-synonymous c.G868A, leading to p.D290N. Each of these mutations occurred in one case. With regard to the samples that were wild type for these V-ATPase variants, at least two samples presented variants in genes that are part of endosomal/lysosomal/autophagosomal networks including ABCA8, ABCC6, AGAP3, ATG9A, CTSB, DNAJC13, GALC, NPC1, SLC15A3, SLC31A2, and TMEM104. CONCLUSION: Although the mechanisms involved in oral GCT initiation and progression remain unclear, our results suggest that oral GCTs have V-ATPase variants similarly to GCTs from other tissues/organs, and additionally show variants in lysosomes/endosomes/autophagosomal genes.

KRAS mutations drive adenomatoid odontogenic tumor and are independent of clinicopathological features.

Adenomatoid odontogenic tumor is a benign encapsulated epithelial odontogenic tumor that shows an indolent clinical behavior. We have reported in a few adenomatoid odontogenic tumors mutations in KRAS, which is a proto-oncogene frequently mutated in cancer such as lung, pancreas, and colorectal adenocarcinomas. We aimed to assess KRAS mutations in the hotspot codons 12, 13, and 61 in a large cohort of adenomatoid odontogenic tumors and to test the association of these mutations with clinical (age, site, tumor size, follicular/extrafollicular subtypes) and histopathological parameters. Thirty eight central cases were studied. KRAS codon 12 mutations were assessed by TaqMan allele-specific qPCR (p.G12V/R) and/or Sanger sequencing, and codon 13 and 61 mutations were screened by Sanger. Histological tumor capsule thickness was evaluated by morphometric analysis. Additionally, the phosphorylated form of the MAPK downstream effector ERK1/2 was investigated. Statistical analysis was carried out to test the association of KRAS mutations with clinicopathological parameters. KRAS c.35 G >T mutation, leading to p.G12V, was detected in 15 cases. A novel mutation in adenomatoid odontogenic tumor, c.34 G >C, leading to p.G12R, was detected in 12 cases and the other 11 were wild-type. Codon 12 mutations were not associated with the clinicopathological parameters tested. RAS mutations are known to activate the MAPK pathway, and we show that adenomatoid odontogenic tumors express phosphorylated ERK1/2. In conclusion, a high proportion of adenomatoid odontogenic tumors (27/38, 71%) have KRAS codon 12 mutations, which occur independently of the clinicopathological features evaluated. Collectively, these findings indicate that KRAS mutations and MAPK pathway activation are the common features of this tumor and some cancer types. Although it is unclear why different codon 12 alleles occur in different disease contexts and the complex interactions between tumor genotype and phenotype need clarification, on the basis of our results the presence of KRAS p.G12V/R favors the adenomatoid odontogenic tumor diagnosis in challenging oral neoplasm cases.

The long noncoding RNA KIAA0125 is upregulated in ameloblastomas.

Ameloblastoma and adenomatoid odontogenic tumor (AOT) are jaw tumors derived from the teeth forming apparatus. While ameloblastoma is a destructive, debilitating lesion, with conventional surgical treatment leading to facial deformity and morbodities, AOT shows indolent clinical behavior. The underlying molecular mechanisms associated with their biological behavior are unknown. The use of high-density whole-genome microarray analysis in ameloblastomas and AOT revealed high frequency of genomic gain at 14q32.33, which encompasses the long noncoding RNA (lncRNA) gene KIAA0125. In the present study, we aimed to investigate the expression profile of KIAA0125 in these tumors. Thirteen samples were included (five solid/multicystic ameloblastomas, four AOT, and four dental follicles). The relative quantification of KIAA0125 expression was obtained by qPCR and interactions of KIAA0125 were in silico predicted. We detected higher levels of KIAA0125 transcripts in the ameloblastoma group compared to dental follicles (p = 0.042). The expression levels of KIAA0125 in AOT were not different from that of dental follicles. KIAA0125 was predicted to interact with 41 miRNA families. Four miRNAs of these families have been previously reported differentially expressed in ameloblastoma, being miR-135a-5p, miR-204-5p and miR-205-5p upregulated, and miR-150-5p downregulated. The lncRNA KIAA0125 is likely involved in the ameloblastoma pathobiology. LncRNAs hold strong promise as therapeutic targets and experimental validation of this lncRNA functions may lead to tailored therapies targeting KIAA0125 in extensive and recurrent ameloblastoma cases.

Absence of BRAFV600E mutation in odontogenic keratocysts.

BACKGROUND: Mutations in the patched 1 (PTCH1) gene are the main genetic alteration reported in sporadic and nevoid basal cell carcinoma-associated odontogenic keratocyst (OKC). Oncogenic mutations, including BRAFV600E, previously considered exclusive of malignant neoplasms have been reported in odontogenic tumors. Recently, a high frequency of BRAFV600E mutation has been reported in OKC. Because of the considerable recurrence rate of OKC, the identification of druggable genetic mutations can be relevant in the management of extensive lesions. METHODS: A set of 28 OKCs was included in this work. Initially, 10 sporadic and eight OKC samples from four NBCCS patients (a pair of lesions from each syndromic patient) were submitted to targeted next-generation sequencing (NGS) of 2800 different mutations in 50 oncogenes and tumor suppressor genes, including BRAF. Ten extra sporadic OKC samples were included to assess BRAFV600E mutation using TaqMan allele-specific qPCR. RESULTS: The following missense mutations occurred in one case each: ATM p.Ser333Phe, SMO p.Gly416Glu, PIK3CA p.Ser326Phe, FBXW7 p.Ser438Phe, JAK2 p.Ser605Phe, PTEN p.Arg173His, ATM p.Cys353Arg, PTEN p.Ser294Arg, MET p.His1112Tyr. None of the 18 samples showed the BRAFV600E (or any other V600) mutation in the NGS. BRAFV600E mutation was detected by qPCR in one of the 10 OKC. Collectively, our results show BRAFV600E mutation in 1 of 28 OKC cases. CONCLUSION: On the basis of our results, OKCs do not present recurrent hotspot mutations in these 50 genes commonly mutated in cancer. In addition, BRAFV600E does not play a central role in OKC pathogenesis.

Cancer genes mutation profiling in calcifying epithelial odontogenic tumour.

AIMS: To identify calcifying epithelial odontogenic tumour (CEOT) mutations in oncogenes and tumour suppressor genes. METHODS: A panel of 50 genes commonly mutated in cancer was sequenced in CEOT by next-generation sequencing. Sanger sequencing was used to cover the region of the frameshift deletion identified in one sample. RESULTS: Missense single nucleotide variants (SNVs) with minor allele frequency (MAF) <1% were detected in PTEN, MET and JAK3. A frameshift deletion in CDKN2A occurred in association with a missense mutation in the same gene region, suggesting a second hit in the inactivation of this gene. APC, KDR, KIT, PIK3CA and TP53 missense SNVs were identified; however, these are common SNVs, showing MAF >1%. CONCLUSION: CEOT harbours mutations in the tumour suppressor PTEN and CDKN2A and in the oncogenes JAK3 and MET. As these mutations occurred in only one case each, they are probably not driver mutations for these tumours.

The Wnt/ß-catenin pathway is deregulated in cemento-ossifying fibromas.

OBJECTIVE: The molecular pathogenesis of cemento ossifying fibroma (COF) is unclear. The purpose of this study was to investigate mutations in 50 oncogenes and tumor suppressor genes, including APC and CTNNB1, in which mutations in COF have been previously reported. In addition, we assessed the transcriptional levels of the Wnt/ß-catenin pathway genes in COF. STUDY DESIGN: We used a quantitative polymerase chain reaction array to evaluate the transcriptional levels of 44 Wnt/ß-catenin pathway genes in 6 COF samples, in comparison with 6 samples of healthy jaws. By using next-generation sequencing (NGS) in 7 COF samples, we investigated approximately 2800 mutations in 50 genes. RESULTS: The expression assay revealed 12 differentially expressed Wnt/ß-catenin pathway genes in COF, including the upregulation of CTNNB1, TCF7, NKD1, and WNT5 A, and downregulation of CTNNBIP1, FRZB, FZD6, RHOU, SFRP4, WNT10 A, WNT3 A, and WNT4, suggesting activation of the Wnt/ß-catenin signaling pathway. NGS revealed 5 single nucleotide variants: TP53 (rs1042522), PIK3 CA (rs2230461), MET (rs33917957), KIT (rs3822214), and APC (rs33974176), but none of them was pathogenic. CONCLUSIONS: Although NGS detected no oncogenic mutation, deregulation of key Wnt/ß-catenin signaling pathway genes appears to be relevant to the molecular pathogenesis of COF.

Targeted next-generation sequencing of glandular odontogenic cyst: a preliminary study.

OBJECTIVE: Glandular odontogenic cyst (GOC) is an uncommon developmental cyst. Its molecular pathogenesis is unclear, and deep sequencing may help identify causative low-frequency variants in tumors. We investigated in GOC mutations in 50 genes commonly altered in human cancers. STUDY DESIGN: Targeted next-generation sequencing was used to interrogate a panel of approximately 2800 mutations in GOC. RESULTS: Six missense single nucleotide variations (SNVs) were reported. Three SNVs (TP53 rs1042522, KDR rs1870377, and KIT rs3822214) are listed as "common single-nucleotide polymorphisms" at the UCSC Genome Browser. The other SNVs (PIK3CA p.Glu689Lys, PIK3CA p.Ala708Thr, and TP53 p.Leu289Phe) are predicted to have deleterious or damaging effects on proteins, but they showed very low frequency in our samples and could not be further validated by orthogonal methods. CONCLUSIONS: No pathogenic SNV was detected in this cohort of GOCs. Further studies with larger gene panels or whole exome sequencing are needed to find the genetic basis of GOC.

Next-generation sequencing of oncogenes and tumor suppressor genes in odontogenic myxomas.

BACKGROUND: Mutations previously considered drivers of malignant neoplasms also occur in benign tumors. From the biological perspective, the study of malignant and benign neoplasms is equally relevant. The study of rare tumors contributes to the understanding of the more common ones, as both could share the same hallmark genetic drivers. The identification of driver mutations in benign tumors is facilitated by the fact that they harbor quiet genomes. Pathogenic mutations have being described in benign epithelial odontogenic tumors, such as ameloblastomas and adenomatoid odontogenic tumors. However, the molecular pathogenesis of odontogenic myxoma (OM), a benign aggressive ectomesenchymal tumor, is still poorly characterized, precluding the development of personalized therapy. Aiming to find druggable genetic mutations, we investigated in OM mutations in 50 genes commonly mutated in cancer. METHODS: We used targeted next-generation sequencing to interrogate over 2,800 COSMIC mutations in OM. RESULTS: Missense single nucleotide variants were detected in KDR, TP53, PIK3CA, KIT, JAK3; however, these did not include pathogenic mutations. CONCLUSION: These aggressive tumors do not harbor pathogenic mutations in genes commonly mutated in human cancers or if they do, these mutations probably occur in a low proportion of cases.

Cohesin subunits, STAG1 and STAG2, and cohesin regulatory factor, PDS5b, in oral squamous cells carcinomas.

BACKGROUND: Cohesin complex is responsible for sister chromatid cohesion. STAG1/STAG2 is part of the complex, which is regulated by PDS5B. Alterations in these genes were described in tumors. PDS5B is a negative regulator of cell proliferation. We aimed to assess molecular alterations in these genes in oral squamous cell carcinoma (OSCC) and predict their expression by the expression of 84 cell cycle genes. In addition, we investigated whether pds5b protein expression impacted ki-67 and p53 immunopositivity. METHODS: We assessed loss of heterozygosity (LOH) at STAG1 and STAG2 loci in 15 OSCC using three polymorphic markers. Associations between the immunoexpression of pds5b and ki-67 and p53 were tested in 62 samples. Differences between transcriptional levels of STAG1, STAG2, and PDS5B between OSCC and normal oral mucosa (NM) were evaluated by qPCR. An 84 cell cycle genes qPCR array was carried with OSCC samples, and STAG1, STAG2, and PDS5B were independently used as response variables in multiple linear regression models. RESULTS: Loss of heterozygosity in at least one marker was observed in three samples. pds5b, p53, and ki-67 were highly expressed, and no association was found between pds5b immunoexpression and ki-67 or p53 (P > 0.05). OSCC and NM showed similar transcriptional levels of STAG1, STAG2, and PDS5B. STAG1 and CUL3 expression seem to be related (P = 0.004). CONCLUSIONS: There is LOH at STAG1 and STAG2 loci in OSCC, but OSCC and NM showed similar transcriptional levels of STAG1, STAG2, and PDS5B. pds5b immunoexpression in OSCC was high, but it was not associated with proliferation cell index.