Comment la taille d'un organisme est-elle régulée au cours du développement embryonnaire ? Quels sont les mécanismes génétiques à l'origine de l'arrêt de la prolifération pendant la croissance d'un organisme pluricellulaire ? Afin d'identifier des acteurs de la sortie du cycle cellulaire au cours du développement, mon travail s’est orienté sur l’étude de gènes suppresseurs de tumeurs pendant la croissance du toit optique (TO) du médaka Oryzias latipes. Le TO, structure dorsale du cerveau moyen des Vertébrés, est un modèle particulièrement adapté à l’étude de la régulation de la prolifération. Trois zones de la marge vers le centre du TO sont discernables : une zone périphérique de prolifération, une zone intermédiaire de cellules sortant du cycle cellulaire et une zone centrale de cellules différenciées. Un crible d'expression par hybridation In Situ a été réalisé et a permis d'identifier 28 gènes exprimés dans le TO, suggérant leur implication dans le contrôle de la sortie du cycle cellulaire au cours du développement. Dans le but de caractériser in vivo la fonction de gènes issus de ce crible, le gène BTG1 (B-cell Translocation Gene 1) et les membres de sa famille, ont été étudiés au cours du développement du médaka. J’ai mené des expériences fonctionnelles sur BTG1, permettant de mettre en évidence son rôle central pour la morphogenèse du système nerveux central. De plus, une autre partie de mon travail s’est penchée sur l’étude de l’expression des membres de la voie de signalisation Hippo, bien connue et caractérisée chez la drosophile et les Mammifères pour son rôle dans le contrôle de la taille des organes via une régulation de l’arrêt de la prolifération. A l’issu de notre travail, une fonction de la voie de signalisation Hippo dans la formation du TO et des somites a pu être mise en évidence au cours du développement du médaka. / How is an organisms’ size regulated during embryonic development? What are the genetic mechanisms that control the proliferation arrest during multicellular organisms growth? In order to identify a cell cycle exit developmental actor genes, I have analysed the role of tumor suppressor genes (TSGs) in the optic tectum (OT) of the medaka Oryzias latipes. This structure is particularly suited for this kind of studies because, during its morphogenesis, there is a strict correlation between the position of a cell and its degree of differentiation. 3 zones can be easily distinguished from the border to the center: a marginal zone made of proliferative cells, an intermediate zone in which cells exit the cycle, and a central zone made of postmitotic cells. Using this criterium, I have performed an in situ hybridization expression screen on 150 TSGs on medaka embryos. The expression patterns of 28 TSGs in the OT suggest their implication in the OT proliferation arrest mechanisms. I focused my study on the BTG1 gene, implicated in many cancers, and for which few developmental data are available. A functional analysis on developing medaka embryos has been performed and permitted to highlight the essential role of BTG1 in central nervous system morphogenesis. Furthermore, I performed an expression study on Hippo signalling pathway components. Hippo pathway is well caracterised for its organ size control function in drosophila and Mammals. Our results show that this pathway could act in OT formation and somitogenesis in medaka fish.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-06-06T13:59:11Z No. of bitstreams: 1 VALDEMIR DA SILVA BRITO - TESE (PPGEE) 2016.pdf: 24283842 bytes, checksum: 359b3901fbb8d95187c4a580e505a74f (MD5) / Made available in DSpace on 2018-06-06T13:59:11Z (GMT). No. of bitstreams: 1 VALDEMIR DA SILVA BRITO - TESE (PPGEE) 2016.pdf: 24283842 bytes, checksum: 359b3901fbb8d95187c4a580e505a74f (MD5) Previous issue date: 2016-10-07 / Capes / Este trabalho propõe um modelo elétrico de supressor de surto de ZnO que o representa com exatidão nas três regiões de operação, em uma ampla faixa de frequência e amplitude. O Modelo Elétrico Proposto (MEP) foi validado a partir de um banco de dados, contendo resultados de medições de tensão e corrente. Este banco de dados é constituído por medições em doze varistores de ZnO de cinco fabricantes diferentes, com diferentes dimensões físicas e características elétricas. Nos ensaios, os varistores foram submetidos a diversos níveis de tensão na região de baixas correntes. Também foram aplicados aos varistores vários níveis de amplitude de impulsos de corrente de manobra (30/60 µs), descarga atmosférica (8/20 µs), alta corrente (4/10 µs) e impulsos de corrente com frentes de onda mais rápidas (1,5/26 µs e 3/6 µs), abordando as regiões altamente não linear e altas correntes. Adicionalmente, outros ensaios foram realizados com objetivo de verificar a presença do acoplamento indutivo e a influência do invólucro do supressor de surto na medição da tensão residual. A partir do banco de dados, foram realizadas simulações com o MEP, e com os modelos Convencional e IEEE, já consolidados no meio científico. Os resultados dos modelos foram comparados entre si, e com os resultados de medição. O MEP apresentou melhores resultados em praticamente todos os casos, nas três regiões de operação. O MEP também foi avaliado em estudos reais de energização de linha de transmissão, rejeição de carga e coordenação de isolamento. Os resultados de simulação dos estudos apresentaram níveis de amplitude condizentes com o esperado, e não apresentaram oscilações numéricas ou instabilidade. Os parâmetros do MEP são de fácil determinação, e todas as informações necessárias estão contidas nos datasheets dos fabricantes. / This work proposes an electric model of ZnO surge arresters that represents accurately the ZnO surge arresters in a wide range of frequencies and amplitudes. The Proposed Electric Model (PEM) was validated from a database, containing results of voltage and current measurements. This database are based in twelve ZnO varistors of five different manufacturers, with different physical dimensions and electrical characteristics. In the lab tests, the varistors were submitted to different voltage levels in the low current region. There were also applied to the varistors multilevel amplitude of switching current impulses (30/60 µs), lightning current impulses (8/20 µs), high current impulses (4/10 µs) and current impulses with very fast front time (1.5/26 µs and 3/6 µs), addressing the highly nonlinear and high current regions. In addition, other lab tests were conducted in order to verify the presence of inductive coupling and the infuence of the surge arrester housing in the residual voltage measuring. From the database, simulations were performed with the PEM, with the Conventional and IEEE models which are already consolidated in the scientific community. The results of the models were compared among themselves, and with the measurement results. The PEM presented best results in practically all cases, in all three operating regions. The PEM was also evaluated in real studies of transmission line energization, load shedding and insulation coordination. The simulation results of the studies presented amplitude levels as expected and did not presented numerical oscillations or instability. The PEM parameters are easily determined, besides that all necessary information is contained in the manufacturers datasheet.

O fenômeno de vibração induzida por vórtices (VIV) é particularmente danoso para estruturas submarinas como risers de exploração de petróleo. A maneira mais usual de se atenuarem os efeitos de VIV é instalar um supressor, como por exemplo strakes ou fairings. Dentre esses, foi desenvolvido por All Brow Universal Components um supressor chamado Ventilated Trousers (VT), que consiste em uma malha permeável feita de uma rede flexível e dezenas de bobbins. Através de um estudo experimental, procurou-se investigar os mecanismos hidrodinâmicos pelos quais o supressor V T funciona. Foram construídos três modelos diferentes de supressores: um modelo idêntico ao V T e duas malhas dele derivadas, alterando-se a geometria dos bobbins e a distribuição destes ao redor da malha. Foram realizados ensaios com o modelo xo e ensaios de VIV em um grau de liberdade alterando-se o amortecimento estrutural. Foram medidos deslocamento e forças de sustentação e arrasto. Os resultados mostraram que o supressor do tipo V T reduz as amplitudes de vibração, força de sustentação e arrasto quando comparados com um cilindro oscilando. No entanto, aumenta a força de arrasto quando comparado com o cilindro xo. A geometria da malha mostrou-se de grande importância para a supressão de VIV. Modelos que possuem o disco externo no bobbin impedem o surgimento de folga entre o modelo e o cilindro, além de aumentar o amortecimento hidrodinâmico. Três hipóteses foram levantadas para explicar o funcionamento do supressor V T. A primeira diz que a supressão é provocada pelo aumento do amortecimento hidrodinâmico. Os ensaios mostraram que, de fato, o supressor V T aumenta o amortecimento e, consequentemente, diminui as VIV. No entanto, somente esse efeito não explica toda a supressão obtida. As outras hipóteses, relacionadas à alterações bi e tridimensionais da esteira, foram avaliadas, porém não se pode afirmar que alguma delas seja isoladamente responsável por produzir o mecanismo hidrodinâmico de supressão. / The phenomenon of vortex-induced vibration (VIV) is particularly harmful to submarine structures such as risers used for oil extraction. The most usual way to attenuate the effects of VIV is the installation of suppressors, like strakes or fairings. Among them, All Brow Universal Components developed a VIV suppressor called Ventilated Trousers (VT), which consist of a permeable mesh made of a flexible net and tens of bobbins. Three different models of suppressors based on permeable meshes have been assembled with the objective to understand the hydrodynamic mechanism behind the suppression: one model identical to the VT and two meshes with different bobbin geometries and distribution. Tests were carried out with xed models and models free to oscillate in one degree of freedom varying the structural damping. Displacements, drag and lift forces were measured. Results showed that the VT suppressor reduced vibration amplitudes, lift and drag forces when compared to an oscillating circular cylinder. However, it increased drag force when compared to a fixed circular cylinder. The mesh geometry proved to be important to VIV suppression. Models that had an external disc on the bobbins avoided the appearance of a gap between the model and the cylinder. Three hypotheses were formulated to explain how the VT suppressor works. The first one says that the increase on hydrodynamic damping is responsible for suppression. In fact, tests showed that the VT increased hydrodynamic damping and, consequently, reduced the VIV response. However, this effect alone does not explain the suppression as a whole. The other two hypotheses related to two-dimensional and three-dimensional wake changes were evaluated, but it cannot be stated that any of them, on its own, is responsible for the whole of the suppression mechanism.

The offshore oil industry is engaged in the development of new floating platforms, such as Spar, semi-submersible, tension-leg, FPSO and monocolumn for the exploration of deep and ultra-deep waters. Some of these floating systems have circular cross sections (or cross sections of other bluff geometries) being susceptible to vortex-induced vibrations (VIV). Vortex shedding behind a bluff body can be altered, suppressed or controlled over a limited range of Reynolds numbers. Various flow-control techniques, which result in the reduction of drag and unsteady forces, have been suggested and tested in simple geometries. One such method is the moving-surface boundary layer control (MSBC), in which smaller control rotating cylinders are placed close to the bluff body. This method is considered as an inspiration for the present experimental investigation of VIV suppression for omni-directional flows. In this context, three different configurations have been assembled to compare the effect of suppression on a plain cylinder surrounded by two, four and eight control cylinders distributed symmetrically around it. Experiments were carried out with static models and models free to oscillate in one-degree-of-freedom with fixed and rotating control cylinders. Experiments with a plain cylinder were performed to serve as reference. Displacements, drag and lift forces were measured. The position of the control cylinders proved to be an important parameter to VIV suppression. Configurations with two control cylinders increased lift and drag forces. In contrast, configurations of four and eight control cylinders showed to be more effective to suppress VIV. Furthermore the results for all the cases of the configuration of eight fixed control cylinders presented a reduction of displacement amplitude, lift and drag forces when compared to a plain cylinder. However, when the control cylinders were actuated, the two cases with rotating control cylinders increased drag force when compared to fixed control cylinders. / A indústria offshore está envolvida no desenvolvimento de novas plataformas flutuantes como Spar, semi-submersível, TLP, FPSO e monocoluna para a exploração de águas profundas e ultra-profundas. Alguns destes sistemas flutuantes têm seções transversais circulares (ou de outras seções rombudas) sendo susceptíveis à vibrações induzidas por vórtices (VIV). A esteira de vórtices desprendida de um corpo rombudo pode ser alterada ou suprimida ao longo de uma faixa de número de Reynolds. Várias técnicas de controle do escoamento foram sugeridas e testadas em geometrias simples, resultando na redução de forças de sustentação e arrasto. Um desses métodos é o controle de camada limite por superfícies móveis (CCLSM), no qual cilindrinhos rotativos de controle são colocados próximos ao corpo rombudo. Neste trabalho, este método foi abordado através de uma investigação experimental como um supressor de VIV para o escoamento omnidirecional. Neste escopo três diferentes configurações foram montadas para comparar o efeito de supressão sobre um cilindro liso rodeado por dois, quatro e oito cilindros de controle, distribuídos simetricamente em torno dele. Foram realizados ensaios com o modelo estático, ensaios de VIV em um grau de liberdade com cilindros de controle fixos e rotativos. Foram medidos deslocamento e forças de sustentação e arrasto. Os resultados mostraram que a posição dos cilindros de controle é um parâmetro importante para a supressão de VIV. A configuração com dois cilindros de controle aumentou as forças de sustentação e arrasto. Diferentemente, as configurações de quatro e oito cilindros de controle mostraram-se mais eficazes para suprimir VIV. Além disso, todos os casos da configuração de oito cilindros de controle fixos apresentaram redução nas amplitudes de vibração e nas forças de sustentação e arrasto, quando comparados com um cilindro liso. No entanto, quando os cilindros de controle foram acionados para rotacionar, mostrou-se um aumento na força de arrasto em relação aos cilindros de controle fixos.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O carcinoma gÃstrico à a segunda causa de morte por cÃncer no mundo. No Cearà à o segundo mais freqÃente entre os homens e o terceiro entre as mulheres. Dos cÃnceres gÃstricos os adenocarcinomas representam em torno de 95%. A doenÃa tem sido associada a fatores genÃticos e ambientais sendo demonstrada Ãntima relaÃÃo com a infecÃÃo por Helicobacter pylori, principalmente associada à presenÃa do gene cagA e genÃtipos vacAs1m1. Entretanto, apesar dos mecanismos pelos quais a bactÃria promove a carcinogÃnese gÃstrica ainda nÃo estarem esclarecidos, uma das hipÃteses seria atravÃs da inativaÃÃo de supressores tumorais. O objetivo do presente trabalho foi verificar, em adenocarcinomas gÃstricos, se a presenÃa de H. pylori, e de seus genes cagA e vacA, està relacionada com a mutaÃÃo e/ou alteraÃÃo na expressÃo protÃica dos supressores tumorais p53 e p27. Neste estudo, 74 amostras de pacientes foram analisadas quanto à presenÃa de H. pylori, cagA+ e os genÃtipos de vacA, pela reaÃÃo em cadeia da polimerase (PCR). A anÃlise mutacional do gene p53 foi realizada por PCR-SSCP e a detecÃÃo da mutaÃÃo/superexpressÃo do p53 e expressÃo da proteÃna p27 pelo mÃtodo imunohistoquÃmico. A bactÃria foi detectada em 95% das amostras, das quais 63% eram cagA(+). Dentre os alelos de vacA, observou-se predomÃnio de s1 (74%) e m1 (82%), associados em 69% dos casos. Na anÃlise mutacional do p53 verificou-se que 72% dos casos exibiram alteraÃÃo no padrÃo de mobilidade eletroforÃtica, sendo esta associada significativamente à presenÃa do gene cagA. Por outro lado, apenas 29% dos casos apresentaram detecÃÃo pelo mÃtodo imunohistoquÃmico, nÃo sendo encontrada associaÃÃo com a H. pylori. A proteÃna p27 demonstrou acentuada reduÃÃo em sua expressÃo (detectada em apenas 19% dos casos), nÃo demonstrando atividade compensatÃria em relaÃÃo à proteÃna p53 mutada e sem associaÃÃo estatÃstica dos casos negativos com a presenÃa da H. pylori. Finalmente, os resultados sugerem que estes supressores simultaneamente inativados podem ser o ponto chave da desregulaÃÃo do ciclo celular que, associados a outros fatores, favoreÃam o desenvolvimento e progressÃo dos adenocarcinomas gÃstricos. Hà indÃcios de que a presenÃa bacteriana, e dos seus genes cagA(+) e vacA/s1m1, possam influenciar, de forma nÃo esclarecida, as alteraÃÃes moleculares ocorridas nos supressores tumorais p53 e p27. / Gastric carcinoma is the second cause of death by cancer in the world. On State of Ceara-Brazil is the second most frequent type of cancer in men and third in women. Adenocarcinomas account for approximately 95% of all malignant gastric neoplasms. It has been associated to genetic and environmental factors and a intimate relationship between the infection by the bacteria Helicobacter pylori and the gastric carcinoma have been related. The presence of the cagA gene and specific genotypes (s1m1) of the gene vacA have been detected in more pathogenic strains. Although the precise molecular mechanisms by which H. pylori could promote the process of gastric carcinogenesis are under investigation, one hypothesized mechanism involves the tumor supressor genes inactivation. The aim of the present study was to verify if the presence of Helicobacter pylori, cagA and vacA genes is related to mutations in the tumor supressor gene p53 and altered expression of p53 and p27 proteins in gastric adenocarcinomas. Seventy-four (74) samples were analyzed to detect the presence of H. pylori, cagA and genotypes of vacA by Polymerization Chain Reaction (PCR). The mutational analysis of p53 gene was performed by PCR-SSCP (Polymerization Chain Reaction for analysis of the Single-strand Conformation Polymorphism). Analysis of mutation or overexpression of p53 protein and p27 expression was detected by the immunohistochemical method. The bacteria was detected in 95% of the samples, 63% was cagA(+). Among the vacA allele it was observed prevalence of s1 (74%) and m1 (82%), associated in 69% of the cases. Mutation analysis of p53 demonstrated 72% of the cases with altered electrophoretic mobility; The alterations were significatively more frequent in the presence of the cagA gene. Immunohistochemical analysis detected only 29% of cases with the expression of p53 protein. The protein p27 showed accentuated reduction in its expression (detected in only 19% of the cases), it has not demonstrated compensatory activity in relation to the p53 altered protein, neither association to H. pylori presence. Finally, these data suggest that simultaneous inactivation of these tumor suppressors genes may be the key point of deregulation of the cellular cycle that, associated to the other factors, favor the development and progression of the gastric cancer. There is some evidence that the bacterial presence, cagA and vacA/s1m1 genes, may influence, in a not understood way, the alterations observed in the tumor suppressors p53 and p27.

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No description available.

Autosomal recessive primary microcephaly (MCPH) is a congenital neurodevelopmental disorder characterised by a reduced occipital-frontal head circumference (OFC) of less than -3 SDs below the population mean for age and sex. It is a genetically heterogeneous disorder caused by mutations in one of the following 10 MCPH genes: MCPH1 (microcephalin 1), WDR62 (WD repeat domain 62), CDK5RAP2 (cyclin-dependent kinase 5 regulatory associated protein 2), CASC5 (cancer susceptibility candidate 5), CEP152 (centrosomal protein 152 kDa), ASPM (asp [abnormal spindle] homolog, microcephaly associated [Drosophila]), CENPJ (centromeric protein J), STIL (SCL/TAL1-interrupting locus), CEP135 (centrosomal protein 135 kDa) and CEP63 (centrosomal protein 135 kDa). The MCPH1 (microcephalin 1) gene is located on chromosome 8p23.1. Microsatellite analysis has previously shown LOH at the markers D8S518 and D8S277 flanking the MCPH1 locus in 1/21 oral tumors. Furthermore, LOH at the markers D8S1742 and D8S277 flanking the MCPH1 locus has also been observed in 2/32 hepatocellular carcinomas. MCPH1 has been found to be mutated in breast and endometrial cancers. Additionally, it was found to be downregulated at the transcript level in 19/30 ovarian cancer tissues and the protein level in 93/319 breast cancer tissues. Decreased MCPH1 protein levels are associated with triple negative breast cancers and a lower transcript level of MCPH1 correlates with lesser time for metastasis to occur in breast cancer patients. Interestingly, MCPH1 knockout mice in a null TP53 background show susceptibility to cancer.So far, studies have indicated that MCPH1 is a DNA repair protein. MCPH1 is required for the formation of DNA repair foci, chromatin relaxation, HR and NHEJ. It regulates G1/S and G2/M cell cycle checkpoints. Also, depletion of MCPH1 leads to genomic instability and centrosome amplification. Hence, the defect in the function of MCPH1 can lead to plethora of anomalies including cancer. Based on these observations, we hypothesized that MCPH1 may also function as a tumor suppressor (TS) gene, in addition to its role in the brain development. The purpose of this study was to test if MCPH1 also functions as a TS gene using different approaches in OSCC (oral squamous cell carcinoma). OSCC is the sixth most common type of cancer. It includes the cancer of the lips, anterior 2/3rd of the tongue, buccal mucosa, floor of the mouth, retromolar trigone and gingiva. Despite the advances in the treatment of oral cancer, the five-yr survival rate has not increased. Hence, the effective treatment of OSCC requires the identification of molecular targets to design appropriate therapeutic strategies. LOH, mutations and promoter methylation in tumors are the hallmarks of TS genes. In order to ascertain the TS roles of MCPH1, we carried out LOH analysis in 81 matched blood/normal and tumor oral tissues using D8S1819, D8S277 and D8S1798 markers flanking the MCPH1 locus. The results showed LOH at one or more markers in 14/71 (19.72%) informative samples across the tumor stages from T1 to T4. The entire coding region and the exon-intron junctions of the MCPH1 gene were sequenced for mutations in 15 OSCC samples and 5 cancer cell lines (viz., A549, HeLa, KB, SCC084 and SCC131). In total, three mutations namely c.1561G>T(p.Glu521X), c.321delA(p.Lys107fsX39) and c.1402delA(p.Thr468fsX32) were identified. The expression of MCPH1 was analysed at both the transcript and protein levels by real-time quantitative RT-PCR and immunohistochemistry, respectively, in OSCC samples. MCPH1 was downregulated in 51.22% (21/41) of OSCC samples at the transcript level. The MCPH1 protein was downregulated in 76% (19/25) of the OSCC samples. In order to elucidate if the MCPH1 promoter was methylated in OSCC tissues, we retrieved the MCPH1 promoter from the database TRED (Transcriptional Regulatory Element Database). The promoter was analysed for the presence of CpG islands using the CpG Plot/CpG Report program. Two CpG islands (CpGI and CpGII) were identified within the MCPH1 promoter. Both the CpG islands were analysed for methylation in 40 OSCC samples by COBRA (Combined Bisulfite Restriction Analysis). CpGI showed no methylation in 40 OSCC samples. However, CpGII showed methylation in 4/40 (10%) OSCC samples and the methylation was absent in their corresponding normal oral tissues. To analyse the methylation of the MCPH1 promoter in cancer cell lines, HeLa, KB, SCC084 and SCC131 cells were treated with 5’-2-deoxy azacytidine (AZA), a methyltrasferase inhibitor. HeLa and KB cells did not show any change in the MCPH1 transcript level after the AZA treatment. However, SCC084 and SCC131 cells showed upregulation of MCPH1 after the treatment, suggesting methylation of the MCPH1 promoter. To validate these observations, we examined the methylation status of both the CpG islands in these cell lines. We found methylation of CpGII only in SCC084 cells. HeLa, KB and SCC131 cells showed no methylation of CpGI and CpGII. The results obtained by COBRA in these cell lines were further confirmed by bisulfite sequencing of CpGI and CpGII islands. Further, the upregulation of MCPH1 after azacytidine treatment in SCC131 cells can be attributed to a promoter independent mechanism or due to methylation of the CpG sites not examined by us. To elucidate the biological effects of MCPH1 in a cancer cell line, we generated stable clones overexpressing MCPH1 in KB cells. The results showed that MCPH1 overexpression decreased cellular proliferation, cell invasion, anchorage-independent growth in soft-agar and tumor growth in nude mice. Further, MCPH1 overexpression lead to apoptosis. A low frequency of LOH, mutations and promoter methylation suggested that they might not be the major mechanisms of downregulation of MCPH1 in OSCC. We then speculated that MCPH1 could be regulated by miRNAs. We therefore used five miRNA target prediction softwares to identify miRNAs targeting MCPH1. The programs identified two binding sites for miR-27a within the 5.4 kb region of the 3’-UTR of MCPH1. The luciferase assay showed that both the seed regions of MCPH1 were binding to miR-27a. In addition, transient transfection of the premiR-27a construct in KB cells decreased the protein level of MCPH1. Additionally, in a small panel of 10 OSCC samples, there was a negative correlation between the levels of miR-27a and MCPH1. To the best of our knowledge, this is the first report showing any miRNA regulating the MCPH1 gene. It is important to note that tumor suppressors can serve as potential biomarkers with prognostic value. Hence, we analysed the correlation of the expression levels of MCPH1 with clinico-pathological parameters such as TNM, gender, age and site of the cancer by Fischer’s exact test. No statistical correlation was observed between the transcript or protein levels with any of the clinico-pathological parameters. In summary, the results of the present study have suggested that the primary microcephaly gene MCPH1 shows several hallmarks of TS genes and functions as a tumor suppressor in OSCC, in addition to its role in brain development. We have for the first time shown that miR-27a targets MCPH1 and regulates its level. It is interesting to note that none of the other 10 MCPH genes have been shown to be regulated by any miRNA yet. Our study will be useful in designing novel therapeutic methods for the treatment of OSCC either by overexpression of MCPH1 or reducing the level of miR-27a by an antagomir.