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Arupa Ganguly

Publications and source records attributed to Arupa Ganguly.

At least 19 recordsLinked to original sources
PubMed2006

Prenatal diagnosis and postnatal management of diffuse congenital hyperinsulinism: a case report.

We present the first case of the prenatal diagnosis of congenital hyperinsulinism based on the genetic analysis of known family mutations in the SUR1 gene. An amniocentesis was performed at 16 weeks gestation at which time two mutations in the SUR1 gene were identified consistent with the diagnosis of diffuse hyperinsulinism. The mother was transported to our facility and underwent an elective caesarian section at 38 weeks gestation. The diagnosis was confirmed and treatment was initiated within the first minutes of life. After a short course of failed medical management, the patient underwent a 98% pancreatectomy with subsequent good glycemic control. This case highlights the benefits of the timely in utero diagnosis of hyperinsulinism by mutational analysis.

ATP-Binding Cassette Transporters↗
PubMed2006

Novel mutations in ENG and ACVRL1 identified in a series of 200 individuals undergoing clinical genetic testing for hereditary hemorrhagic telangiectasia (HHT): correlation of genotype with phenotype.

Hereditary hemorrhagic telangiectasia (HHT; Osler-Weber-Rendu disease) is an autosomal dominant disease characterized by arteriovenous malformations ranging from cutaneous and mucous membrane telangiectasias to more severe pulmonary, gastrointestinal, and cerebral arteriovenous malformations (AVMs). Acute complications from bleeding or pulmonary shunting may be catastrophic. However, when diagnosed early, the complications can usually be prevented. Mutations in two genes, Endoglin (ENG) and activin receptor-like kinase 1 (ACVRL1 or ALK1) have been associated with HHT. We describe the results of mutation analysis on a consecutive series of 200 individuals undergoing clinical genetic testing for HHT. The observed sensitivity of mutation detection was similar to that in other series with strict ascertainment criteria. A total of 127 probands were found, with sequence changes consisting of 103 unique alterations, 68 of which were novel. In addition, eight intragenic rearrangements in the ENG gene and two in the ACVRL1 gene were identified in a subset of coding sequence mutation-negative individuals. Most individuals tested could be categorized by the number of HHT diagnostic criteria present. Surprisingly, almost 50% of the cases with a single symptom were found to have a significant sequence alteration; three of these reported only nosebleeds. Genetic testing can confirm the clinical diagnosis in individuals and identify presymptomatic mutation carriers. As many of the complications of HHT disease can be prevented, a confirmed molecular diagnosis provides an opportunity for early detection of AVMs and management of the disease.

Activin Receptors, Type II↗
PubMed2006

Molecular and immunohistochemical analyses of the focal form of congenital hyperinsulinism.

Congenital hyperinsulinism is a rare pancreatic endocrine cell disorder that has been categorized histologically into diffuse and focal forms. In focal hyperinsulinism, the pancreas contains a focus of endocrine cell adenomatous hyperplasia, and the patients have been reported to possess paternally inherited mutations of the ABCC8 and KCNJ11 genes, which encode subunits of an ATP-sensitive potassium channel (K(ATP)). In addition, the hyperplastic endocrine cells show loss of maternal 11p15, where imprinted genes such as p57(kip2) reside. In order to evaluate whether all cases of focal hyperinsulinism are caused by this mechanism, 56 pancreatectomy specimens with focal hyperinsulinism were tested for the loss of maternal allele by two methods: immunohistochemistry for p57(kip2) (n=56) and microsatellite marker analysis (n=27). Additionally, 49 patients were analyzed for K(ATP) mutations. Out of 56 focal lesions, 48 demonstrated clear loss of p57(kip2) expression by immunohistochemistry. The other eight lesions similarly showed no nuclear labeling, but the available tissue was not ideal for definitive interpretation. Five of these eight patients had paternal K(ATP) mutations, of which four demonstrated loss of maternal 11p15 within the lesion by microsatellite marker analysis. All of the other three without a paternal K(ATP) mutation showed loss of maternal 11p15. K(ATP) mutation analysis identified 32/49 cases with paternal mutations. There were seven patients with nonmaternal mutations whose paternal DNA material was not available, and one patient with a mutation that was not present in either parent's DNA. These eight patients showed either loss of p57(kip2) expression or loss of maternal 11p15 region by microsatellite marker analysis, as did the remaining nine patients with no identifiable K(ATP) coding region mutations. The combined results from the immunohistochemical and molecular methods indicate that maternal 11p15 loss together with paternal K(ATP) mutation is the predominant causative mechanism of focal hyperinsulinism.

ATP-Binding Cassette Transporters↗
PubMed2005

A novel KCNJ11 mutation associated with congenital hyperinsulinism reduces the intrinsic open probability of beta-cell ATP-sensitive potassium channels.

The beta-cell ATP-sensitive potassium (KATP) channel controls insulin secretion by linking glucose metabolism to membrane excitability. Loss of KATP channel function due to mutations in ABCC8 or KCNJ11, genes that encode the sulfonylurea receptor 1 or the inward rectifier Kir6.2 subunit of the channel, is a major cause of congenital hyperinsulinism. Here, we report identification of a novel KCNJ11 mutation associated with the disease that renders a missense mutation, F55L, in the Kir6.2 protein. Mutant channels reconstituted in COS cells exhibited a wild-type-like surface expression level and normal sensitivity to ATP, MgADP, and diazoxide. However, the intrinsic open probability of the mutant channel was greatly reduced, by approximately 10-fold. This low open probability defect could be reversed by application of phosphatidylinositol 4,5-bisphosphates or oleoyl-CoA to the cytoplasmic face of the channel, indicating that reduced channel response to membrane phospholipids and/or long chain acyl-CoAs underlies the low intrinsic open probability in the mutant. Our findings reveal a novel molecular mechanism for loss of KATP channel function and congenital hyperinsulinism and support the importance of phospholipids and/or long chain acyl-CoAs in setting the physiological activity of beta-cell KATP channels. The F55L mutation is located in the slide helix of Kir6.2. Several permanent neonatal diabetes-associated mutations found in the same structure have the opposite effect of increasing intrinsic channel open probability. Our results also highlight the critical role of the Kir6.2 slide helix in determining the intrinsic open probability of KATP channels.

Animals↗
PubMed2005

Regulation of NKT cell development by SAP, the protein defective in XLP.

The adaptor molecule SAP is expressed in T lymphocytes and natural killer (NK) cells, where it regulates cytokine production and cytotoxicity. Here, we show that SAP, encoded by the SH2D1A gene locus, also has a crucial role during the development of NKT cells, a lymphocyte subset with immunoregulatory functions in response to infection, cancer and autoimmune disease. Following stimulation with the NKT cell-specific agonist alpha-galactosyl ceramide (alphaGC), Sh2d1a-/- splenocytes did not produce cytokines or activate other lymphoid lineages in an NKT cell-dependent manner. While evaluating the abnormalities in alphaGC-induced immune responses, we observed that Sh2d1a-/- animals lacked NKT cells in the thymus and peripheral organs. The defect in NKT cell ontogeny was hematopoietic cell autonomous and could be rescued by reconstitution of SAP expression within Sh2d1a-/- bone marrow cells. Seventeen individuals with X-linked lymphoproliferative disease (XLP), who harbored germline mutations in SH2D1A, also lacked NKT cells. Furthermore, a female XLP carrier showed completely skewed X chromosome inactivation within NKT cells, but not T or B cells. Thus, SAP is a crucial regulator of NKT cell ontogeny in humans and in mice. The absence of NKT cells may contribute to the phenotypes of SAP deficiency, including abnormal antiviral and antitumor immunity and hypogammaglobulinemia.

Animals↗
PubMed2005

Sensitive multistep clinical molecular screening of 180 unrelated individuals with retinoblastoma detects 36 novel mutations in the RB1 gene.

Retinoblastoma (RB) is a neoplasm of retinal origin caused by mutations in RB1, the retinoblastoma tumor suppressor gene. To facilitate genetics counseling and patient management, we adopted a multistep molecular screening assay for detecting RB1 mutations. This assay included DNA sequencing to identify mutations within coding exons and immediate flanking intronic regions, Southern blot analysis to characterize genomic rearrangements, and transcript analysis to characterize potential splicing mutations buried within introns. In a pilot investigation of 180 patients from North America, we identified germline RB1 mutations in 77 out of 85 bilateral RB patients (91%), 7 out of 10 familial unilateral (70%), and 6 out of 85 unilateral patients with no family history of RB (7%). Mutations included 36 novel alterations spanning the entire RB1 gene. Seven of these novel changes were missense or silent mutations. Sequence analysis predicted that, in five out of seven cases, the changes can cause aberrant splicing. This was confirmed by transcript analysis in four out of five cases. In addition, four intronic point mutations within nonconsensus sites activated cryptic splice sites. Without the transcript analysis, the significance of these 11 mutations would have remained undefined. In a separate investigation of a subset of unilateral RB tumors, we identified somatic biallelic RB1 gene inactivation in 34 out of 56 cases (61%) cases. In 14 tumors, only one of the two RB1 mutations could be detected, and in eight tumors, no mutations were detected. The absence of detectable RB1 mutations in eight bilateral cases and eight unilateral tumors suggests that alternative genetic mechanisms may underlie the development of RB in certain individuals.

DNA Mutational Analysis↗
PubMed2004

Genotype-phenotype correlations in children with congenital hyperinsulinism due to recessive mutations of the adenosine triphosphate-sensitive potassium channel genes.

Congenital hyperinsulinism (HI) is most commonly caused by recessive mutations of the pancreatic beta-cell ATP-sensitive potassium channel (K(ATP)), encoded by two genes on chromosome 11p, SUR1 and Kir6.2. The two mutations that have been best studied, SUR1 g3992-9a and SUR1 delF1388, are null mutations yielding nonfunctional channels and are characterized by nonresponsiveness to diazoxide, a channel agonist, and absence of acute insulin responses (AIRs) to tolbutamide, a channel antagonist, or leucine. To examine phenotypes of other K(ATP) mutations, we measured AIRs to calcium, leucine, glucose, and tolbutamide in infants with recessive SUR1 or Kir6.2 mutations expressed as diffuse HI (n = 8) or focal HI (n = 14). Of the 24 total mutations, at least seven showed evidence of residual K(ATP) channel function. This included positive AIR to both tolbutamide and leucine in diffuse HI cases or positive AIR to leucine in focal HI cases. One patient with partial K(ATP) function also responded to treatment with the channel agonist, diazoxide. Six of the seven patients with partial defects had amino acid substitutions or insertions; whereas, the other patient was compound heterozygous for two premature stop codons. These results indicate that some K(ATP) mutations can yield partially functioning channels, including cases of hyperinsulinism that are fully responsive to diazoxide therapy.

ATP-Binding Cassette Transporters↗
PubMed2004

Congenital hyperinsulinism: intraoperative biopsy interpretation can direct the extent of pancreatectomy.

Most cases of congenital hyperinsulinism (HI) manifest as either a diffuse or focal form. Diffuse HI is characterized by the presence of enlarged islet cell nuclei, defined as those occupying an area 3 times larger than the surrounding nuclei, throughout the pancreas, and usually requires near total pancreatectomy. Focal HI contains, within an otherwise normal pancreas with islet cell nuclei of normal size, a focus of adenomatous hyperplasia characterized by endocrine cell overgrowth occupying more than 40% of a given area. This form of HI is amenable to partial pancreatectomy. The current study assesses whether intraoperative frozen section evaluation can distinguish the 2 forms and guide the extent of pancreatectomy. By frozen section analysis, diffuse HI is diagnosed when enlarged islet cell nuclei are present in random intraoperative biopsies from the head, body, and tail of the pancreas. Focal HI is suggested when random biopsies contain no large islet cell nuclei, prompting a further search for a focal lesion. Fifty-two HI patients who underwent pancreatectomy from October 1, 1998 to September 30, 2002 were reviewed. On permanent sections, 18 were classified as diffuse HI, 30 had focal HI, and 4 could not be categorized as either. Among 18 diffuse HI patients, 17 were correctly diagnosed by frozen section; all underwent near total pancreatectomy. One case was interpreted as not belonging to typical diffuse or focal HI; however, the permanent sections showed diffuse HI. Twenty-six of 30 focal HI cases were correctly diagnosed by frozen section. The remaining 4 focal HI cases posed diagnostic difficulties on frozen sections because of one the following reasons: 1) presence of equivocally large islet cell nuclei or rare truly large islet cell nuclei in areas nonadjacent to the focal lesion, and 2) large and/or ill defined focus of adenomatous hyperplasia. Twenty-one of 30 focal HI patients eventually had 10% to 93% (mean, 41.8%) of their pancreas resected. In addition to cases typical for diffuse and focal HI, there were 4 other cases whose pancreata did not fit well with either category. These pancreata showed islet cell nuclear enlargement, as characteristically seen in diffuse HI, but only in confined areas of the pancreas. Examination of routinely processed tissue confirmed frozen section findings in all 4 cases. Intraoperative frozen section evaluation, therefore, can assume an essential role in identifying patients with focal HI to limit the extent of pancreatectomy. However, a small number of cases with unusual histology warrant caution when performing frozen section evaluation.

Biopsy↗
PubMed2004

Preoperative evaluation of infants with focal or diffuse congenital hyperinsulinism by intravenous acute insulin response tests and selective pancreatic arterial calcium stimulation.

Infants with congenital hyperinsulinism often require pancreatectomy. Recessive mutations of the ATP-dependent plasma membrane potassium channel (K(ATP)) genes, SUR1 and K(ir)6.2, cause diffuse hyperinsulinism. K(ATP) channel mutations can also cause focal disease through loss of heterozygosity for maternal 11p, resulting in expression of a paternal mutation. This study evaluated whether focal vs. diffuse hyperinsulinism could be diagnosed by acute insulin response (AIR) tests and whether arterial calcium stimulation/venous sampling (ASVS) could localize focal lesions. Fifty infants with diazoxide-unresponsive hyperinsulinism were studied. Focal lesions occurred in 70% of the cases. Positive AIR calcium occurred in 17 of 30 focal and 10 of 13 diffuse cases (P < 0.04). Positive AIR tolbutamide occurred in 27 of 30 focal vs. seven of 13 diffuse cases (P < 0.02); K(ATP) channel mutations were identified in four of the latter. ASVS localized the lesion in 24 of 33 focal cases (73%) but correctly diagnosed diffuse disease in only four of 13 cases. These results indicate that preoperative AIR tests do not distinguish focal vs. diffuse disease because some K(ATP) channel mutations retain responsiveness to tolbutamide. The ASVS test can be used to localize focal lesions in infants. The combination of ASVS, careful intraoperative histologic analysis, and surgical expertise succeeded in correcting hypoglycemia in 86% of the infants with focal hyperinsulinism.

ATP-Binding Cassette Transporters↗
PubMed2004

Familial leucine-sensitive hypoglycemia of infancy due to a dominant mutation of the beta-cell sulfonylurea receptor.

Familial leucine-sensitive hypoglycemia of infancy was described in 1956 as a condition in which symptomatic hypoglycemia was provoked by protein meals or the amino acid, leucine. The purpose of this study was to determine the genetic basis for hypoglycemia in a family diagnosed with leucine-sensitive hypoglycemia in 1960. Recently diagnosed family members showed a dominantly transmitted pattern of diazoxide-responsive hyperinsulinism (HI). However, they did not fit the characteristics of HI caused by glutamate dehydrogenase gene mutations, previously felt to explain leucine-sensitive hypoglycemia. Islet function was examined using acute insulin response (AIR) tests to calcium, leucine, glucose, and tolbutamide as well as oral protein tolerance tests. Five of five affected family members showed an abnormal positive calcium AIR, and two of five showed a positive leucine AIR. Protein-induced hypoglycemia was demonstrated in five of six affected subjects. Mutation analysis of four known HI genes (sulfonylurea receptor 1, Kir6.2, glutamate dehydrogenase, and glucokinase) in family members identified an R1353H missense mutation in exon 33 of SUR1. (86)Rb(+) efflux and electrophysiological studies of R1353H SUR1 coexpressed with wild-type Kir6.2 in COSm6 cells demonstrated partially impaired ATP-dependent potassium channel function. Leucine-sensitive hypoglycemia in this family was found to result from a dominantly expressed SUR1 mutation.

Child, Preschool↗
PubMed2003

TP53, BRCA1, and BRCA2 tumor suppressor genes are not commonly mutated in survivors of Hodgkin's disease with second primary neoplasms.

PURPOSE: Despite recognition that second malignant neoplasms (SMNs) contribute significantly to mortality after the successful treatment of Hodgkin's disease (HD), little is known about the molecular events leading to secondary tumors. Factors contributing to second cancer risk include the carcinogenic effects of ionizing radiation and chemotherapy, in combination with possible host susceptibility. To clarify whether host genetic factors contribute to secondary tumorigenesis, we performed mutational analyses of the TP53, BRCA1, and BRCA2 tumor suppressor genes in a cohort of 44 HD patients developing one or more SMN. PATIENTS AND METHODS: Family cancer histories and constitutional DNA samples were obtained from 44 HD patients with SMNs identified. Using DNA-based sequencing, we evaluated the TP53 gene in all 44 patients. Nineteen female patients developing one or more secondary breast cancer were also analyzed for mutations in the BRCA1 and BRCA2 breast cancer-susceptibility genes. RESULTS: Nineteen patients (43%) had more than one SMN, and 12 patients (27%) had a positive family history of cancer. One of 44 patients tested for TP53 harbored a novel homozygous germline abnormality. One of 19 patients tested for BRCA2 carried a previously described heterozygous inactivating mutation. We identified no germline BRCA1 mutations. CONCLUSION: Despite features suggestive of genetic predisposition, the TP53, BRCA1, and BRCA2 genes were not frequently mutated in this cohort of HD patients developing SMNs. Larger studies of these genes or investigations of other genes involved in cellular DNA damage response pathways may identify host genetic factors that contribute to secondary tumorigenesis.

Adult↗
PubMed2003

Exon skipping caused by an intronic insertion of a young Alu Yb9 element leads to severe hemophilia A.

Short interspersed elements, such as Alu elements, have propagated to more than one million copies in the human genome. They affect the genome in several ways, caused by retrotransposition, recombination between elements, gene conversion, and alterations in gene expression. These events, including novel insertions into active genes, have been associated with a number of human disorders. Hemophilia A is an X-linked severe bleeding disorder and is caused by mutations in the Factor VIII gene. The spectrum of mutations includes point mutations, rearrangements, insertions, and deletions. Recently, an Alu retrotransposition event in a coding exon has been reported in a family with a severe form of hemophilia A. This was the first report of an Alu insertion in the Factor VIII gene. Here, we report a second Alu insertion event that lies in an intron of the same gene that causes exon skipping and the complete disruption of gene expression.

Alternative Splicing↗
PubMed2003

Clinical and molecular characterization of a dominant form of congenital hyperinsulinism caused by a mutation in the high-affinity sulfonylurea receptor.

Recessive mutations of sulfonylurea receptor 1 (SUR1) and potassium inward rectifier 6.2 (Kir6.2), the two adjacent genes on chromosome 11p that comprise the beta-cell plasma membrane ATP-sensitive K(+) (K(ATP)) channels, are responsible for the most common form of congenital hyperinsulinism in children. The present study was undertaken to identify the genetic defect in a family with dominantly inherited hyperinsulinism affecting five individuals in three generations. Clinical tests were carried out in three of the patients using acute insulin responses (AIRs) to intravenous stimuli to localize the site of defect in insulin regulation. The affected individuals showed abnormal positive calcium AIR, normal negative leucine AIR, subnormal positive glucose AIR, and impaired tolbutamide AIR. This AIR pattern suggested a K(ATP) channel defect because it resembled that seen in children with recessive hyperinsulinism due to two common SUR1 mutations, g3992-9a and delPhe1388. Genetic linkage to the K(ATP) locus was established using intragenic polymorphisms. Mutation analysis identified a novel trinucleotide deletion in SUR1 exon 34 that results in the loss of serine 1387. Studies of delSer1387 in COSm6 cells confirmed that the expressed mutant protein assembles with Kir6.2 and trafficks to the plasma membrane, but it had no (86)Rb efflux ion transport activity. These results indicate that hyperinsulinism in this family is caused by a SUR1 mutation that is expressed dominantly rather than recessively.

ATP-Binding Cassette Transporters↗
PubMed2002

Multiple primary melanoma revisited.

BACKGROUND: Incidence of cutaneous melanoma continues to increase in the Caucasian population worldwide. Approximately 5% of melanoma patients develop additional primary melanoma. This rate is significantly higher than the estimated lifetime risk of an individual for developing the disease (1.4%). These features suggest that a genetic predisposition may underlie multiple primary melanomas (MPMs). Prior studies had identified CDKN2A mutations in a few MPM individuals. The objectives of this study were to determine the frequency of family history of melanoma in MPM cases, to characterize other clinical features including history of other cancer, and to determine the association with functional CDKN2A mutations. METHODS: This study used a case series design. All living patients who had been seen in the Pigmented Lesion Clinic at the University of Pennsylvania and who had more than one primary invasive malignant melanoma or an invasive primary followed by an in situ melanoma were eligible for participation. RESULTS: Individuals with MPM frequently had a family history of melanoma, dysplastic nevi (DN), and/or another cancer including basal cell carcinoma (BCC), and squamous cell carcinoma breast cancer, and a personal history of DN, and basal cell carcinoma. Germline mutations in CDKN2A gene were identified in 8 of 96 MPM cases (8.3%, 95% confidence interval, 6.7-9.9%). CONCLUSIONS: These data indicate that the presence of MPM is associated with a modest incidence of a family history of melanoma, DN, or BCC and a small association with CDKN2A mutations. Therefore, in addition to the MPM index case, other family members can benefit from screening and regular surveillance for melanoma, DN, and BCC.

Adolescent↗
PubMed2002

An update on conformation sensitive gel electrophoresis.

Conformation-sensitive gel electrophoresis (CSGE) was developed as a method of heteroduplex analysis to screen large multi-exon genes for sequence variation. The novelty of the method was in the use of a non-proprietary acrylamide gel matrix that used 1,4-bis (acrolyl) piperazine (BAP) as a cross linker with ethylene glycol and formamide as mildly denaturing solvents. The denaturing environment enhances the conformation polymorphism present in DNA heteroduplexes containing variations as small as single nucleotide polymorphisms (SNPs). CSGE has also been adapted for use on a fluorescent platform (F-CSGE) that resulted in higher throughput and sensitivity. Variation in sensitivity of CSGE has been studied extensively. The results demonstrate that the nature of the mismatched base in a defined sequence context has the most profound effect on the conformation of the heteroduplex. Additionally, the size of the PCR product, as well as the location of the mismatch within the PCR product, are two important parameters that determine the resolution of the mismatch-containing heteroduplexes during CSGE. Like any other mutation scanning technique, CSGE can have limited resolution of two closely linked sequence variations. For specific genes, like BRCA1 and BRCA2 where multiple SNPs are present in the coding sequence, each CSGE shift has to be sequenced to define the exact nature of the sequence change. In conclusion, CSGE scanning provides a powerful, cost-efficient way to scan genes with high sensitivity and specificity.

Base Sequence↗
PubMed2002

High throughput mutation screening of the factor VIII gene (F8C) in hemophilia A: 37 novel mutations and genotype-phenotype correlation.

Hemophilia A (HEMA) is an X-linked bleeding disorder caused by mutations in the factor VIII gene (F8C). Molecular genetic testing for the factor VIII gene is challenging due to its large size. Here we present results of high throughput mutation scanning based on Southern blot analysis and direct sequencing of all PCR amplified coding exons and the exon-intron boundaries of the factor VIII gene. The results of mutation analysis on 89 hemophiliac males showed presence of a disease-causing mutation in 80 individuals (90%, 95% CI of 82%-95%). Seven out of nine mutation-negative individuals were severe cases of hemophilia A with < 1% factor VIII protein in the blood. The correlation of phenotype with genotype as observed in this study was not absolute. This finding is supported by similar observations in the international database for hemophilia A mutations (HAMSTeRS). This issue raises the importance of genotypes at other loci that can act as modifiers for the phenotype. Thirty-four novel mutations and three novel substitutions for previously reported amino acid residues were identified in this series of 80 mutations. The mutations cover the full spectrum including rearrangements, deletions, frameshift, and point mutations. The novel missense mutations require careful evaluation. Prediction of a mutation as the disease-causing allele was made from the nature of the substitution and the degree of conservation of the mutated amino acid among species that have diverged in evolution. In some cases segregation analysis of the mutation with disease condition was performed when other family members were available.

Child↗