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ABSTRACT: Hirschsprung disease (HSCR) is a congenital disease characterized by the absence of ganglion cells in various length of distal digestive tract. The rearranged during transfection gene (RET) is considered the major gene in HSCR. Although an increasing number of HSCR-associated RET coding sequence (CDS) mutations have been identified in recent years, not many have been investigated for functional consequence on the RET protein.
We examined the functional implications of the de novo RET-CDS mutations V145G, Y483X, V636fsX1, and F961L that we first identified in sporadic Chinese patients with HSCR. The V145G disrupted RET glycosylation and F961L RET phosphorylation. Presumably, the truncation mutations would affect the translocation or the anchoring of the RET protein onto the cellular membrane.
The study of RET-CDS mutations that appear de novo is essential not only for understanding the mechanistic of the disease but also for penetrance and recurrence risk estimations, being the ultimate goal for the improvement in disease management and counseling.
Birth Defects Research Part A Clinical and Molecular Teratology 12/2011; 94(1):47-51. · 2.27 Impact Factor
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Maria-Mercè Garcia-Barceló,
Xiaoping Miao,
Clara S Tang,
Hon-Cheong So,
Waikiu Tang, Thomas Y Y Leon,
Manting So,
Benjamin Yip,
Ronald Y L Chen,
Eric F C Cheung,
Eric Y H Chen,
Tao Li,
Paul Tam,
Stacey S Cherny,
Pak C Sham
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ABSTRACT: NRG1 is one of the best-supported schizophrenia (SZ) susceptibility genes. A NRG1 V266L missense mutation has been found to be associated with SZ in several populations. V266L is not in linkage disequilibrium with any of the SZ-associated NRG1 haplotypes described thus far, and may represent an independent SZ susceptibility locus within NRG1 gene. V266 is a highly conserved residue and its substitution is predicted to have a deleterious effect on the protein. As there are no data for V266L in Chinese, and given the potential relevance of this mutation, we investigated the V266L prevalence in 270 Chinese patients with schizophrenia and 270 ethnically matched controls. V266L was found neither in patients nor in controls. Lack of replication of an association across populations may be because of the differences in linkage disequilibrium structure or allele frequencies. Some true associations may not be replicated regardless of the sample size of the study.
Psychiatric genetics 10/2010; 21(1):47-9. · 2.33 Impact Factor
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ABSTRACT: Hirschsprung's disease (HSCR) is a congenital disorder associated with the lack of intramural ganglion cells in the myenteric and sub-mucosal plexuses along varying segments of the gastrointestinal tract. The RET gene is the major gene implicated in this gastrointestinal disease. A highly recurrent mutation in RET (RET(R114H)) has recently been identified in approximately 6-7% of the Chinese HSCR patients which, to date, has not been found in Caucasian patients or controls nor in Chinese controls. Due to the high frequency of RET(R114H) in this population, we sought to investigate whether this mutation may be a founder HSCR mutation in the Chinese population.
To test whether all RET(R114) were originated from a single mutational event, we predicted the approximate age of RET(R114H) by applying a Bayesian method to RET SNPs genotyped in 430 Chinese HSCR patients (of whom 25 individuals had the mutation) to be between 4-23 generations old depending on growth rate. We reasoned that if RET(R114H) was a founder mutation then those with the mutation would share a haplotype on which the mutation resides. Including SNPs spanning 509.31 kb across RET from a recently obtained 500 K genome-wide dataset for a subset of 181 patients (14 RET(R114H) patients), we applied haplotype estimation methods to determine whether there were any segments shared between patients with RET(R114H) that are not present in those without the mutation or controls. Analysis yielded a 250.2 kb (51 SNP) shared segment over the RET gene (and downstream) in only those patients with the mutation with no similar segments found among other patients.
This suggests that RET(R114H) is a founder mutation for HSCR in the Chinese population.
PLoS ONE 01/2010; 5(6):e10918. · 4.09 Impact Factor
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ABSTRACT: The rearranged during transfection (RET) gene encodes a single-pass receptor whose proper expression and function are essential for the development of enteric nervous system. Mutations in RET regulatory regions are also associated with Hirschsprung disease (HSCR) (aganglionosis of the colon). We previously showed that 2 polymorphisms in RET promoter are associated with the increased risk of HSCR. These single nucleotide polymorphisms overlap with the NK2 homeobox 1 (Nkx2-1) binding motif interrupting the physical interaction of NKX2-1 with the RET promoter and result in reduced RET transcription. In this study, we further delineated Nkx2-1-mediated RET Transcription.
First, we demonstrated that PHOX2B, like SOX10 and NKX2-1, is expressed in the mature enteric ganglions of human gut by immunohistochemistry. Second, subsequent dual-luciferase-reporter studies indicated that Nkx2-1 indeed works coordinately with Phox2b and Sox10, but not Pax3, to mediate RET transcription. In addition, identification of Phox2b responsive region in RET promoter further provides solid evidence of the potential functional interaction between Phox2b and RET.
In sum, Phox2b and Sox10 act together with Nkx2.1 to modify RET signaling and this interaction may also contribute to HSCR susceptibility.
Journal of Pediatric Surgery 10/2009; 44(10):1904-12. · 1.45 Impact Factor
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Elly S W Ngan,
Brian H H Lang,
Tingting Liu,
Cathy K Y Shum,
Man-Ting So,
Danny K C Lau, Thomas Y Y Leon,
Stacey S Cherny,
Sophia Y Tsai,
Chung-Yau Lo,
Ui-Soon Khoo,
Paul K H Tam,
Maria-Mercè Garcia-Barceló
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ABSTRACT: The genetic factors that determine the risk of papillary thyroid carcinoma (PTC) among patients with multinodular goiter (MNG) remain undefined. Because thyroid transcription factor-1 (TTF-1) is important to thyroid development, we evaluated whether the gene that encodes it, TITF-1/NKX2.1, is a genetic determinant of MNG/PTC predisposition.
Twenty unrelated PTC patients with a history of MNG (MNG/PTC), 284 PTC patients without a history of MNG (PTC), and 349 healthy control subjects were screened for germline mutation(s) in TITF-1/NKX2.1 by sequencing of amplified DNA from blood. The effects of the mutation on the growth and differentiation of thyroid cells were demonstrated by ectopic expression of wild-type (WT) and mutant proteins in PCCL3 normal rat thyroid cells, followed by tests of cell proliferation, activation of cell growth pathways, and transcription of TTF-1 target genes. All statistical tests were two-sided.
A missense mutation (1016C>T) was identified in TITF-1/NKX2.1 that led to a mutant TTF-1 protein (A339V) in four of the 20 MNG/PTC patients (20%). These patients developed substantially more advanced tumors than MNG/PTC or PTC patients without the mutation (P = .022, Fisher exact test). Notably, this germline mutation was dominantly inherited in two families, with some members bearing the mutation affected with MNG, associated with either PTC or colon cancer. The mutation encoding the A339V substitution was not found among the 349 healthy control subjects nor among the 284 PTC patients who had no history of MNG. Overexpression of A339V TTF-1 in PCCL3 cells, as compared with overexpression of WT TTF-1, was associated with increased cell proliferation including thyrotropin-independent growth (average A339V proliferation rate = 134.27%, WT rate = 104.43%, difference = 34.3%, 95% confidence interval = 12.0% to 47.7%, P = .010), enhanced STAT3 activation, and impaired transcription of the thyroid-specific genes Tg, TSH-R, and Pax-8.
This is the first germline mutation identified in MNG/PTC patients. It could contribute to predisposition for MNG and/or PTC and to the pathogenesis of PTC.
CancerSpectrum Knowledge Environment 02/2009; 101(3):162-75. · 14.07 Impact Factor
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Vincent C H Lui,
William W C Cheng, Thomas Y Y Leon,
Danny K C Lau,
Maria-Mercedes Garcia-Barcelo,
Maria-Mercedes Garcia-Bareclo,
Xiao P Miao,
Mandy K M Kam,
Man T So,
Yan Chen,
Nancy A Wall,
Mai H Sham,
Paul K H Tam
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ABSTRACT: The enteric nervous system (ENS) controls intestinal peristalsis, and defective development of this system results in hypo/aganglionosis, as seen in Hirschsprung's disease. In the embryo, vagal neural crest cells (NCC) migrate and colonize the intestine rostrocaudally then differentiate into the ganglia of the ENS. Vagal NCC express the homeobox gene Hoxb5, a transcriptional activator, in human and mouse, so we used transgenic mice to investigate the function of Hoxb5 and the receptor tyrosine kinase gene Ret, which is affected in many patients with Hirschsprung's disease, in ENS development.
We perturbed the Hoxb5 pathway by expressing a chimeric protein enb5, in which the transcription activation domain of Hoxb5 was replaced with the repressor domain of the Drosophila engrailed protein (en), in vagal NCC. This enb5 transcriptional repressor competes with wild-type Hoxb5 for binding to target genes, exerting a dominant negative effect.
We observed that 30.6% +/- 2.3% of NCC expressed enb5 and that these enb5-expressing NCC failed to migrate to the distal intestine. A 34%-37% reduction of ganglia (hypoganglionosis) and slow peristalsis and, occasionally, absence of ganglia and intestinal obstruction were observed in enb5-expressing mice. Ret expression was markedly reduced or absent in NCC and ganglia, and enb5 blocked Hoxb5 induction of Ret in neuroblastoma cells.
Our data indicate that Ret is a downstream target of Hoxb5 whose perturbation causes Ret haploinsufficiency, impaired NCC migration, and hypo/aganglionosis, suggesting that Hoxb5 may contribute to the etiology of Hirschsprung's disease.
Gastroenterology 04/2008; 134(4):1104-15. · 11.68 Impact Factor
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Clinical Chemistry 09/2005; 51(8):1552-4. · 7.91 Impact Factor
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Mercè Garcia-Barcelo,
Raymond W Ganster,
Vincent C H Lui, Thomas Y Y Leon,
Man-Ting So,
Anson M F Lau,
Ming Fu,
Mai-Har Sham,
Joanne Knight,
Maria Stella Zannini,
Pak C Sham,
Paul K H Tam
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ABSTRACT: Single nucleotide polymorphisms (SNPs) of the coding regions of receptor tyrosine kinase gene (RET) are associated with Hirschsprung's disease (HSCR, aganglionic megacolon). These SNPs, individually or combined, may act as a low penetrance susceptibility locus and/or be in linkage disequilibrium (LD) with another susceptibility locus located in RET regulatory regions. Because two RET promoter SNPs have been found associated with HSCR, in LD with HSCR-associated RET coding region haplotypes, their implication in the transcriptional regulation of RET is of major interest. Analysis of 172 sporadic HSCR patients also revealed the presence of HSCR-associated RET promoter SNPs in LD with the main coding region RET haplotype observed in Chinese patients. By using a weighted logistic regression approach, we determined that of all SNPs tested in our study, the promoter SNPs are the most correlated to the disease. Functional analysis of the RET promoter SNPs in the context of additional 5' regulatory regions demonstrated that the HSCR-associated alleles decrease RET transcription. These SNPs overlap a TTF-1 binding site and TTF-1-activated RET transcription is also decreased by the HSCR-associated SNPs. Moreover, we identified an HSCR patient with a Gly322Ser TTF-1 mutation that compromises activation of transcription from HSCR-associated RET promoter haplotypes. Interestingly, we show that the pattern of RET and TTF-1 expression is coincident in developing human gut. We also present a detailed profile of the RET gene in our population, which provides an insight into the higher incidence of the disease in China.
Human Molecular Genetics 02/2005; 14(2):191-204. · 7.64 Impact Factor
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ABSTRACT: BackgroundThe rearranged during transfection (RET) gene encodes a single-pass receptor whose proper expression and function are essential for the development of enteric nervous system. Mutations in RET regulatory regions are also associated with Hirschsprung disease (HSCR) (aganglionosis of the colon). We previously showed that 2 polymorphisms in RET promoter are associated with the increased risk of HSCR. These single nucleotide polymorphisms overlap with the NK2 homeobox 1 (Nkx2-1) binding motif interrupting the physical interaction of NKX2-1 with the RET promoter and result in reduced RET transcription. In this study, we further delineated Nkx2-1–mediated RET Transcription.Methods and resultsFirst, we demonstrated that PHOX2B, like SOX10 and NKX2-1, is expressed in the mature enteric ganglions of human gut by immunohistochemistry. Second, subsequent dual-luciferase-reporter studies indicated that Nkx2-1 indeed works coordinately with Phox2b and Sox10, but not Pax3, to mediate RET transcription. In addition, identification of Phox2b responsive region in RET promoter further provides solid evidence of the potential functional interaction between Phox2b and RET.ConclusionIn sum, Phox2b and Sox10 act together with Nkx2.1 to modify RET signaling and this interaction may also contribute to HSCR susceptibility.
Journal of Pediatric Surgery.
