Characterisation of the biochemical and cellular roles of native and pathogenic amelogenesis imperfecta mutants of FAM83H

The majority of mutations identified in patients with amelogenesis imperfecta have been mapped to FAM83H. As FAM83H expression is not limited to the enamel, how FAM83H contributes to amelogenesis is still largely unknown. We previously reported that members of the FAM83 family of proteins interact with and regulate the subcellular distribution of the promiscuous serine-threonine protein kinase CK1 family, through their shared N-terminal DUF1669 domains. FAM83H co-localises with CK1 isoforms to speckle-like structures in both the cytoplasm and nucleus. In this report, we show FAM83H, unlike other FAM83 proteins, interacts and colocalises with NCK1/2 tyrosine kinase adaptor proteins. This interaction is mediated by proline-rich motifs within the C-terminus of FAM83H, specifically interacting with the second and third SH3 domains of NCK1/2. Moreover, FAM83H pathogenic AI mutant proteins, which trigger C-terminal truncations of FAM83H, retain their interactions with CK1 isoforms but lose interaction with NCK1/2. These AI mutant FAM83H proteins acquire a nuclear localisation, and recruit CK1 isoforms to the nucleus where CK1 retains its kinase activity. As understanding the constituents of the FAM83H-localised speckles may hold the key to unravelling potential substrates of FAM83H-associated CK1 substrates, we employed a TurboID-based proximity labelling approach and uncovered several proteins including Iporin and BAG3 as potential constituents of the speckles.     

Defining a New Candidate Gene for Amelogenesis Imperfecta: From Molecular Genetics to Biochemistry

Amelogenesis imperfecta is a group of genetic conditions that affect the structure and clinical appearance of tooth enamel. The types (hypoplastic, hypocalcified, and hypomature) are correlated with defects in different stages of the process of enamel synthesis. Autosomal dominant, recessive, and X-linked types have been previously described. These disorders are considered clinically and genetically heterogeneous in etiology, involving a variety of genes, such as AMELX, ENAM, DLX3, FAM83H, MMP-20, KLK4, and WDR72. The mutations identified within these causal genes explain less than half of all cases of amelogenesis imperfecta. Most of the candidate and causal genes currently identified encode proteins involved in enamel synthesis. We think it is necessary to refocus the search for candidate genes using biochemical processes. This review provides theoretical evidence that the human SLC4A4 gene (sodium bicarbonate cotransporter) may be a new candidate gene.     

Long noncoding RNA FAM83H‐AS1 exerts an oncogenic role in glioma through epigenetically silencing CDKN1A (p21)

Gliomas are the commonest and most aggressive primary malignant tumor in the central nervous system. Long noncoding RNAs (lncRNAs) have been identified to act as crucial regulators in multiple biological processes, including tumorigenesis. FAM83H antisense RNA1 (FAM83H‐AS1) has been uncovered to be dysregulated in several cancers. However, the biological role of FAM83H‐AS1 in glioma still needs to be investigated. Currently, our findings indicated that FAM83H‐AS1 was upregulated in glioma tissues and cell lines and high level of FAM83H‐AS1 was associated with poor prognosis of glioma. Loss‐of‐function assays demonstrated that silenced FAM83H‐AS1 obviously suppressed cell proliferation via regulating the cell‐cycle distribution and cell apoptosis rate, and mechanistic experiments revealed that FAM83H‐AS1 could epidemically silence CDKN1A expression through recruiting EZH2 to the promoter of CDKN1A, thereby influencing the cell cycle and proliferation. Collectively, our findings suggested that FAM83H‐AS1 participated in the progression of glioma and might act as a potential therapeutic target and prognosis biomarker for human glioma.     

Whole-Exome sequencing identifies FAM20A mutations as a cause of amelogenesis imperfecta and gingival hyperplasia syndrome

Amelogenesis imperfecta (AI) describes a clinically and genetically heterogeneous group of disorders of biomineralization resulting from failure of normal enamel formation. AI is found as an isolated entity or as part of a syndrome, and an autosomal-recessive syndrome associating AI and gingival hyperplasia was recently reported. Using whole-exome sequencing, we identified a homozygous nonsense mutation in exon 2 of FAM20A that was not present in the Single Nucleotide Polymorphism database (dbSNP), the 1000 Genomes database, or the Centre d'Etude du Polymorphisme Humain (CEPH) Diversity Panel. Expression analyses indicated that Fam20a is expressed in ameloblasts and gingivae, providing biological plausibility for mutations in FAM20A underlying the pathogenesis of this syndrome.     

Suppression of FAM83D Inhibits Glioma Proliferation,Invasion and Migration by Regulating the AKT/mTOR Signaling Pathway

ObjectiveTo explore the mechanism by which the family with sequence similarity 83, member D (FAM83D)-mediated AKT/mTOR signaling pathway activation affects the proliferation and metastasis of glioma cells.MethodsFAM83D protein expression in glioma cells and tissues was detected by western blotting. Glioma U87 and U251 cells were selected and divided into the Mock, siNC, siFAM83D, FAM83D, MK2206 and FAM83D + MK2206 groups. Cell proliferation was assessed by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and clone formation assays, while invasion and migration were evaluated by Transwell assays and wound healing tests. The protein expression of members of the AKT/mTOR pathway was determined via western blotting. Xenograft models were also established in nude mice to observe the in vivo effect of FAM83D on the growth of glioma.ResultsFAM83D was upregulated in glioma patients, especially in those with Stage III-IV. In addition, cells treated with siFAM83D had significant downregulation of p-AKT/AKT and p-mTOR/mTOR, with decreased proliferation and colony numbers, as well as decreased invasion and migration compared to the Mock group. However, FAM83D overexpression could activate the Akt/mTOR pathway and promote the proliferation, invasion and migration of glioma cells. Moreover, treatment with MK2206, an inhibitor of AKT, reversed the promoting effect of FAM83D on the growth of glioma cells. The in vivo experiments demonstrated that silencing FAM83D could inhibit the in vivo growth of glioma cellsConclusionFAM83D was upregulated in glioma and silencing FAM83D suppressed the proliferation, invasion and migration of glioma cells via inhibition of the AKT/mTOR pathway.     

FAM83H-AS1 is associated with clinical progression and modulates cell proliferation,migration, and invasion in bladder cancer

FAM83H-AS1, also known as oncogenic long noncoding RNA (lncRNA)-3, is a novel lncRNA that has been suggested to be dysregulated in a variety of human cancers. However, the expression status and function of FAM83H-AS1 in bladder cancer are still unknown. The object of our study is to explore the clinical value of FAM83H-AS1 in patients with bladder cancer and the biological function of FAM83H-AS1 in bladder cancer cells. In our results, the expression of FAM83H-AS1 was obviously elevated in bladder cancer tissue samples and bladder cancer cell lines compared with adjacent normal tissue samples and normal bladder epithelial cell lines, respectively. In addition, high expression of FAM83H-AS1 was associated with advanced clinical stage and the presence of muscularis invasion and served as an independent poor prognostic factor for overall survival in patients with bladder cancer. The loss-of-function study showed that silencing FAM83H-AS1 expression suppressed cell proliferation, migration, and invasion and induced cycle arrest at G0/G1 phase. In conclusion, FAM83H-AS1 is involved in the progression of bladder cancer and serves as a prognostic biomarker and potential therapeutic target for patients with bladder cancer.     

Genetic Basis of Glycogen Storage Disease Type 1a: Prevalent Mutations at the Glucose-6-Phosphatase Locus

Diagnosis of glycogen storage disease (GSD) type 1a currently is established by demonstrating the lack of glucose-6-phosphatase (G6Pase) activity in the patient's biopsied liver specimen. Recent cloning of the G6Pase gene and identification of mutations within the gene that causes GSD type 1a allow for the development of a DNA-based diagnostic method. Using SSCP analysis and DNA sequencing, we characterized the G6Pase gene of 70 unrelated patients with enzymatically confirmed diagnosis of GSD type 1a and detected mutations in all except 17 alleles (88%). Sixteen mutations were uncovered that were shown by expression to abolish or greatly reduce G6Pase activity and that therefore are responsible for the GSD type 1a disorder. R83C and Q347X are the most prevalent mutations found in Caucasians, 130X and R83C are most prevalent in Hispanics, and R83H is most prevalent in Chinese. The Q347X mutation has thus far been identified only in Caucasian patients, and the 130X mutation has been identified only in Hispanic patients. Our results demonstrate that the DNA-based analysis can accurately, rapidly, and noninvasively detect the majority of mutations in GSD type 1a. This DNA-based diagnosis now permits prenatal diagnosis among at-risk patients and serves as a database in screening and counseling patients clinically suspected of having this disease.     

LncRNA FAM83A-AS1 facilitates tumor proliferation and the migration via the HIF-1α/ glycolysis axis in lung adenocarcinoma

Background: Lung adenocarcinoma (LUAD), the major subtype of lung cancer, is among the leading cause of cancer-related death worldwide. Energy-related metabolic reprogramming metabolism is a hallmark of cancer shared by numerous cancer types, including LUAD. Nevertheless, the functional pathways and molecular mechanism by which FAM83A-AS1 acts in metabolic reprogramming in lung adenocarcinoma have not been fully elucidated.Methods: We used transwell, wound-healing scratch assay, and metabolic assays to explore the effect of FAM83A-AS1 in LUAD cell lines. Western blotting, Co-IP assays, and ubiquitination assays were used to detect the effects of FAM83A-AS1 on HIF-1α expression, degradation, and its binding to VHL. Moreover, an in vivo subcutaneous tumor formation assay was used to detect the effect of FAM83A-AS1 on LUAD.Results: Herein, we identified FAM83A-AS1 as a metabolism-related lncRNA, which was highly correlated with glycolysis, hypoxia, and OXPHOS pathways in LUAD patients using bioinformatics analysis. In addition, we uncovered that FAM83A-AS1 could promote the migration and invasion of LUAD cells, as well as influence the stemness of LUAD cells in vivo and vitro. Moreover, FAM83A-AS1 was shown to promote glycolysis in LUAD cell lines in vitro and in vivo, and was found to influence the expression of genes related to glucose metabolism. Besides, we revealed that FAM83A-AS1 could affect glycolysis by regulating HIF-1α degradation. Finally, we found that FAM83A-AS1 knockdown could inhibit tumor growth and suppress the expression of HIF-1α and glycolysis-related genes in vivo.Conclusion: Our study demonstrates that FAM83A-AS1 contributes to LUAD proliferation and stemness via the HIF-1α/glycolysis axis, making it a potential biomarker and therapeutic target in LUAD patients.     

Craniofacial features associated with amelogenesis imperfecta

Craniofacial alterations occur with increased frequency in patients with amelogenesis imperfecta (AI). The purpose of this study was to characterize the craniofacial features associated with AI in families from the US. Twenty-seven people with AI and 14 unaffected family members from nine separate kindreds were evaluated. The diagnosis was established by history, clinical, and radiographic examination, and histological and or biochemical analysis of enamel. The kindreds were generally classified as hypoplastic AI (HPAI), hypocalcified AI (HCAI), or hypomaturation AI (HMAI) and then further subclassified based on phenotype and mode of inheritance. Linear and angular cephalometric measures were converted to z-scores using gender/age matched values from the Bolton and Behrent's standards. Statistical analyses included t-tests and ANOVA accepting P < or = 0.05 as significant. The vertical dimension of the lower face was significantly increased (ANSMe; P = 0.001), especially in affected individuals compared with unaffected relatives, in all kindreds with HCAI and HMAI but in only one kindred with autosomal recessive rough AI. Clinically, an anterior open bite (overbite < 0 mm) was observed in 26% of all dentate individuals with AI and none of their unaffected relatives. Skeletal morphology was highly variable depending on the AI type and kindred. While this study shows an association of altered craniofacial morphology with certain AI kindreds, the relationship of the AI genotype to the observed malocclusions remains to be defined.     

Hydrophobic helical hairpins: design and packing interactions in membrane environments

Helix-helix interactions within membranes are dominated by van der Waals packing motifs and side chain-side chain hydrogen bond formation, which act in tandem to determine the residues that comprise the interface between two given helices. To explore in a systematic manner the tertiary contacts between transmembrane helices, we have designed and expressed in Escherichia coli highly hydrophobic helix-loop-helix constructs of prototypic sequence K(1)KKKKKKFAIAIAIIAWAX(19)AIIAIAIAIKSPGSKIAIAIAIIAZ(44)AWAIIAIAIAFKKKKKKK(62), where "small" (Ala) and "large" (Ile) residues were used to maximize the tertiary contact area. Evidence that the two transmembrane (TM) segments in the AI construct contain an interface conducive for folding into a hairpin structure was obtained from the results that (i) the single TM AI(pep) peptide derived from the AI hairpin forms SDS-resistant dimers on PAGE gels and (ii) the corresponding sequence forms a strong dimer when examined in vivo in TOXCAT assays. Site-directed mutagenesis of AI hairpins was carried out to incorporate each of the 20 commonly occurring amino acids at X positions. Analysis on Western blots using an oligomerization assay in 12% NuPage-sodium dodecyl sulfate (SDS) indicated that mutants with X = E, D, Q, R, N, H, and K largely formed SDS-resistant dimers-which likely correspond to H-bonded four-helix bundles-while all the others (e.g., X = F, W, L, I, M, V, C, Y, A, T, S, G, and P) remained monomeric. Systematic studies of X/Z double mutants indicated that formation of hairpin dimers is the result of the disruption of stabilizing interactions between the antiparallel helices within the AI construct. The overall results suggest that, in situations where hydrophobic van der Waals packing energy between helices is sufficient to prevent significant rotation about the major axes of interacting helices, intrahairpin side chain-side chain H-bond formation will occur mainly when pairs of polar residues are interfacially located and proximal. Knowledge of the relative contributions of these forces should be of value, for example, in clarifying the context--and the structural consequences--of disease-related mutations.     

The ubiquitin ligase itch is auto-ubiquitylated in vivo and in vitro but is protected from degradation by interacting with the deubiquitylating enzyme FAM/USP9X

Itch is a ubiquitin ligase that has been implicated in the regulation of a number of cellular processes. We previously have identified Itch as a binding partner for the endocytic protein Endophilin and found it to be localized to endosomes. Using affinity purification coupled to mass spectrometry, we have now identified the ubiquitin-protease FAM/USP9X as a binding partner of Itch. The association between Itch and FAM/USP9X was confirmed in vitro by glutathione S-transferase pulldown and in vivo through coimmunoprecipation. Itch and FAM partially colocalize in COS-7 cells at the trans-Golgi network and in peripheral vesicles. We mapped the FAM-binding domain on Itch to the WW domains, a region known to be involved in substrate recognition. However, transient overexpression of FAM/USP9X resulted in the deubiquitylation of Itch. Moreover, we show that Itch auto-ubiquitylation leads to its degradation in the proteasome. By examining the amounts of Itch and FAM in various cell lines and rat tissues, a positive correlation was found in the expression of both proteins. This observation suggests that the levels of FAM expression could have an influence on Itch in cells. Experimental decrease in FAM levels by RNA interference leads to a significant reduction in intracellular levels of endogenous Itch, which can be prevented by treatment with the proteasome inhibitor lactacystin. Accordingly, overexpression of FAM/USP9X resulted in a marked increase in endogenous Itch levels. These results demonstrate an intriguing interplay between a ubiquitin ligase and a ubiquitin protease, based on direct interaction between the two proteins.     

Mutations in FAM111B Cause Hereditary Fibrosing Poikiloderma with Tendon Contracture,Myopathy, and Pulmonary Fibrosis

Congenital poikiloderma is characterized by a combination of mottled pigmentation, telangiectasia, and epidermal atrophy in the first few months of life. We have previously described a South African European-descent family affected by a rare autosomal-dominant form of hereditary fibrosing poikiloderma accompanied by tendon contracture, myopathy, and pulmonary fibrosis. Here, we report the identification of causative mutations in FAM111B by whole-exome sequencing. In total, three FAM111B missense mutations were identified in five kindreds of different ethnic backgrounds. The mutation segregated with the disease in one large pedigree, and mutations were de novo in two other pedigrees. All three mutations were absent from public databases and were not observed on Sanger sequencing of 388 ethnically matched control subjects. The three single-nucleotide mutations code for amino acid changes that are clustered within a putative trypsin-like cysteine/serine peptidase domain of FAM111B. These findings provide evidence of the involvement of FAM111B in congenital poikiloderma and multisystem fibrosis.     

FAM60A,increased by Helicobacter pylori,promotes proliferation and suppresses apoptosis of gastric cancer cells by targeting the PI3K/AKT pathway

Helicobacter pylori (H. pylori) infection can promote the development of gastric cancer (GC); however, the underlying mechanism is not clear. FAM60A has been found showing high levels in some cancer cells, including lung cancer (A549), and pancreatic cancer (Capan-2) cell lines. Data in oncomine showed that FAM60A overexpression was an critical prognostic factor in GC. In this study, we showed that knockdown of FAM60A could revert the increase of proliferation and the decrease of apoptosis caused by H.pylori infection in HGC-27 and AGS cells. Conversely, FAM60A upregulation promoted proliferation and inhibited apoptosis in HGC-27 and AGS cells. We also found that the PI3K/AKT pathway inhibitor LY294002 could revert the changes caused by FAM60A upregulation in HGC-27 and AGS cells. Thus, our study provides evidence that FAM60A act as a carcinogen and suggests that H. pylori-induced upregulation of FAM60A may contribute to the development of gastric cancer.