A clinical and molecular study of a patient with Simpson-Golabi-Behmel syndrome

Prenatal case of Simpson-Golabi-Behmel syndrome with a de novo 370Kb-sized microdeletion of Xq26.2 compassing partial GPC3 gene and review

BACKGROUND

Simpson-Golabi-Behmel syndrome type 1 (SGBS1) is a rare X-linked recessive disorder characterized by pre- and postnatal overgrowth and a broad spectrum of anomalies including craniofacial dysmorphism, heart defects, renal, and genital anomalies. Due to the ultrasound findings are not pathognomonic for this syndrome, most clinical diagnosis of SGBS1 are made postnatally.

METHODS

A pregnant woman with abnormal prenatal sonographic findings was advised to perform molecular diagnosis. Single nucleotide polymorphism array (SNP array) was performed in the fetus, and the result was validated with multiplex ligation-dependent probe amplification (MLPA) and real-time quantitative PCR (qPCR).

RESULTS

The prenatal sonographic presented with increased nuchal translucency at 13 gestational weeks, and later at 21 weeks with cleft lip and palate, heart defect, increased amniotic fluid index and over growth. A de novo 370Kb-deletion covering the 5'-UTR and exon 1 of GPC3 gene was detected in the fetus by SNP array, which was subsequently confirmed by MLPA and qPCR.

CONCLUSION

The de novo 370Kb hemizygous deletion of 5'-UTR and exon 1 of GPC3 results in the SGBS1 of this Chinese family. Combination of ultrasound and genetics tests helped us effectively to diagnose the prenatal cases of SGBS1. Our findings also enlarge the spectrum of mutations in GPC3 gene.

Simpson-Golabi-Behmel syndrome type 1 with subclinical hypothyroidism: A case report

RATIONALE

Simpson-Golabi-Behmel syndrome type 1 (SGBS1) is caused by mutations in GPC3 or in both GPC3 and GPC4. Physical manifestations of SGBS1 include fetal overgrowth and macrostomia, macroglossia. Subclinical hypothyroidism has never been reported in SGBS1 cases.

PATIENT CONCERNS

An 8-days-old boy was referred to our hospital with persistent hypoglycemia and special facies. And the infant showed elevated levels of thyroid-stimulating hormone (TSH). Free T4 and free T3 were normal.

DIAGNOSES

Definitive diagnosis of SGBS1 depends on clinical features and genetic testing. A nonsense mutation (c.1515C > A, p. Cys505*) was tested by whole-exome sequencing.

INTERVENTIONS

Normal blood glucose levels were maintained with glucose infusions. Levothyroxine was given to the patient for treating subclinical hypothyroidism.

OUTCOMES

The parents decided to abandon the treatment of the patient. We learned that the patient died of a lung infection by a telephone follow-up.

LESSONS

Subclinical hypothyroidism could be added to the known clinical manifestations of SGBS1.

Mutation update for the GPC3 gene involved in Simpson-Golabi-Behmel syndrome and review of the literature

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked multiple congenital anomalies and overgrowth syndrome caused by a defect in the glypican-3 gene (GPC3). Until now, GPC3 mutations have been reported in isolated cases or small series and the global genotypic spectrum of these mutations has never been delineated. In this study, we review the 57 previously described GPC3 mutations and significantly expand this mutational spectrum with the description of 29 novel mutations. Compiling our data and those of the literature, we provide an overview of 86 distinct GPC3 mutations identified in 120 unrelated families, ranging from single nucleotide variations to complex genomic rearrangements and dispersed throughout the entire coding region of GPC3. The vast majority of them are deletions or truncating mutations (frameshift, nonsense mutations) predicted to result in a loss-of-function. Missense mutations are rare and the two which were functionally characterized, impaired GPC3 function by preventing GPC3 cleavage and cell surface addressing respectively. This report by describing for the first time the wide mutational spectrum of GPC3 could help clinicians and geneticists in interpreting GPC3 variants identified incidentally by high-throughput sequencing technologies and also reinforces the need for functional validation of non-truncating mutations (missense, in frame mutations, duplications).

Loss-of-function mutations and global rearrangements in GPC3 in patients with Simpson-Golabi-Behmel syndrome

Simpson-Golabi-Behmel syndrome is a congenital malformation syndrome associated with mutations in GPC3, which is located in the Xq26 region. Three new loss-of-function mutations and a global X-chromosome rearrangement involving GPC3 were identified. A female sibling of the patient, who presented with a cleft palate and hepatoblastoma, carries the same chromosomal rearrangement and a paradoxical pattern of X-chromosome inactivation. These findings support variable GPC3 alterations, with a possible mechanism in female patients.

Clinical and oral findings of a patient with Simpson-Golabi-Behmel syndrome

BACKGROUND

The Simpson-Golabi-Behmel syndrome (SGBS) is an overgrowth condition characterised by macrosomia, mental deficiency, large head, prominent skull sutures, midface deficiency, hypertelorism, broad nose, wide mouth, macroglossia, malocclusion, highly arched palate, and musculoskeletal and limb abnormalities. The aim of this case report is to present clinical and oral findings of an 8-year-old boy who had been diagnosed with SGBS.

CASE REPORT

This patient had supernumerary nipples on the right side, cubitus valgus webbed fingers, scoliosis, umbilical hernia, a coarse face, macrocephaly, hypertelorism, a short broad nose, a wide mouth, a straight facial profile and hearing loss. The patient also had macroglossia, diastemas, over-retained primary tooth, absent mandibular permanent central incisors, and highly arched palate. Lateral cephalometric analysis revealed a large anterior cranial base, a large maxilla and mandible, a large inferior face height, and skeletal Class III jaw relationship.

FOLLOW-UP

After extraction of the over-retained primary central tooth, a partial prosthesis was fabricated in order to maintain function. The patient has been recalled regularly at 6-month intervals for 2 years. Over the following years the prosthesis was replaced due to facial growth.

CONCLUSION

Long term follow-up is essential for the patient with SGBS. Preventive dental care, including oral hygiene instructions, diet counselling and the use of fluoride has been implemented.

Phenotypic spectrum of Simpson-Golabi-Behmel syndrome in a series of 42 cases with a mutation in GPC3 and review of the literature

Simpson-Golabi-Behmel syndrome (SGBS) is a rare X-linked multiple congenital abnormality/intellectual disability syndrome characterized by pre- and post-natal overgrowth, distinctive craniofacial features, macrocephaly, variable congenital malformations, organomegaly, increased risk of tumor and mild/moderate intellectual deficiency. In 1996, Glypican 3 (GPC3) was identified as the major gene causing SGBS but the mutation detection rate was only 28-70%, suggesting either genetic heterogeneity or that some patients could have alternative diagnoses. This was particularly suggested by some reports of atypical cases with more severe prognoses. In the family reported by Golabi and Rosen, a duplication of GPC4 was recently identified, suggesting that GPC4 could be the second gene for SGBS but no point mutations within GPC4 have yet been reported. In the genetics laboratory in Tours Hospital, GPC3 molecular testing over more than a decade has detected pathogenic mutations in only 8.7% of individuals with SGBS. In addition, GPC4 mutations have not been identified thus raising the question of frequent misdiagnosis. In order to better delineate the phenotypic spectrum of SGBS caused by GPC3 mutations, and to try to define specific clinical criteria for GPC3 molecular testing, we reviewed the clinical features of all male cases with a GPC3 mutation identified in the two molecular laboratories providing this test in France (Tours and Paris). We present here the results of the analysis of 42 patients belonging to 31 families and including five fetuses and three deceased neonates.

A novel panel of biomarkers in distinction of small well-differentiated HCC from dysplastic nodules and outcome values

Background

Differential diagnosis of high-grade dysplastic nodules (HGDN) and well-differentiated hepatocellular carcinoma (WDHCC) represents a challenge to experienced hepatic clinicians, radiologists and hepatopathologists.

Methods

The expression profiles of aminoacylase-1 (ACY1), sequestosome-1 (SQSTM1) and glypican-3 (GPC3) in low-grade dysplastic nodules (LGDN), HGDN and WDHCC were assessed by immunohistochemistry. The differential diagnostic performances of these three markers alone and in combination for HGDN and WDHCC were investigated by logistic regression models (HGDN = 21; WDHCC = 32) and validated in an independent test set (HGDN, n = 21; WDHCC n = 24). Postoperative overall survival and time to recurrence were evaluated by univariate and multivariate analyses in an independent set of 500 patients.

Results

ACY1, SQSTM1 and GPC3 were differentially expressed in each group. For the differential diagnosis of WDHCC from HGDN, the sensitivity and specificity of the combination of ACY1 + SQSTM1 + GPC3 for detecting WDHCC were 93.8% and 95.2% respectively in the training set, which were higher than any of the three two-marker combinations. The validities of the four diagnostic models were further confirmed in an independent test set, and corresponding good sensitivity and specificity were observed. Interestingly, GPC3 expression in HCC tissues combined with serum α-fetoprotein (AFP) was found to be an independent predictor for overall survival and time to recurrence.

Conclusions

ACY1 + SQSTM1 + GPC3 combination represents a potentially valuable biomarker for distinguishing between WDHCC and HGDN using immunohistochemistry. Meanwhile, low GPC3 staining combined with positive serum AFP may play a practical role in predicting poor postoperative outcome and high tumor recurrence risk.

The Human Obesity Gene Map: The 2003 Update

This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome-wide scans and candidate regions in targeted studies. A total of 35 genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 272 studies reporting positive associations with 90 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, more than 430 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.

The Human Obesity Gene Map: The 2004 Update

This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.

GPC3 mutations in seven patients with Simpson-Golabi-Behmel syndrome

We analyzed mutations of the GPC3gene in seven males with typical manifestations of Simpson-Golabi-Behmel syndrome (SGBS). Genomic DNA was PCR amplified for its all eight exons and exon-intron boundaries using designed set of primers, and PCR products were directly sequenced. All seven males studied had mutations: One patient had a large deletion spanning introns 6 and 7, four each had a C --> T base substitution resulting in a stop codon formation in exons 2, 3, and 4, one had a single-base insertion in exon 2, and the other had a six-base deletion and a three-base insertion in exon 3; all resulting in loss-of-function of the glypican-3 protein. These results, together with previous studies of GPC3 mutations, indicate that there is no hot spot for GPC3 mutations or deletions in the patients with the syndrome. Also, no correlation has been noted between the location and nature of mutations and the phenotype of the patients studied, as is the case of the present study.

The Simpson-Golabi-Behmel syndrome causative glypican-3, binds to and inhibits the dipeptidyl peptidase activity of CD26

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked condition shown to be the result of deletions of the glypican-3 (GPC3) gene. GPC3 is a proteoglycan localized to the cell membrane via a glycosylphosphatidyl-inositol (GPI) anchor. To further elucidate the GPC3 function(s), we have screened various cell lines for proteins that interact with GPC3, resulting in the isolation of a 115 kDa protein, identified as CD26. The interaction occurred with both the glycosylated and unglycosylated forms of GPC3 and led to the inhibition of CD26 peptidase activity. Moreover, introduction of CD26 into Cos-1 cells was accompanied by the up-regulation of cell growth, while inclusion of recombinant GPC3 in the media reduced the growth of CD26 transfected Cos-1 cells, drastically. Furthermore, HepG2 C3A cells containing CD26 underwent apoptosis in the presence of recombinant GPC3 in both concentration and time-dependant manner. In light of the fact that inhibition of CD26 reduces the rate of cell proliferation, we propose that a number of physical findings observed in SGBS patients may be a consequence of a direct interaction of GPC3 with CD26. Furthermore, GPC3 without the GPI anchor is capable of inducing apoptosis indicating that neither the GPI anchor nor the membrane attachment is required for apoptosis induction.

The human obesity gene map: the 2005 update

This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.

Clinical and molecular studies on two further families with Simpson-Golabi-Behmel syndrome

The Simpson-Golabi-Behmel syndrome (SGBS) (OMIM 312870) is an overgrowth/multiple congenital anomalies syndrome caused by a semi-dominant X-linked gene encoding glypican 3 (GPC3). It shows great clinical variability, ranging from mild forms in carrier females to lethal forms with failure to thrive in males. The most consistent findings in SGBS are pre- and postnatal macrosomia, characteristic facial anomalies and abnormalities affecting the internal organs, skeleton, and on some occasions, mental retardation of variable degree. SGBS is also associated with an increased risk of developing embryonal tumors, mostly Wilms and liver tumors. We describe two molecularly-confirmed families with SGBS. All patients had typical manifestations of SGBS including some female relatives who had minor manifestations of the disorder. Some patients had novel findings such as a deep V-shaped sella turcica and six lumbar vertebrae. Molecular studies in affected patients showed a deletion of exon 6 in family 1 and an intronic mutation in family 2.

Craniofacial morphology in a patient with Simpson-Golabi-Behmel syndrome

OBJECTIVE

We present the case of a 6-year-old boy with a coarse face, cleft palate, and malocclusion with anterior open bite who had been diagnosed with Simpson-Golabi-Behmel syndrome. Morphology of the craniofacial structures was examined on the basis of conventional radiographs, three-dimensional (3D) computed tomography (CT) and magnetic resonance (MR) scanning.

PATIENT

This patient had 13 ribs on the right side, slight scoliosis, supernumerary nipples, a coarse face, hypertelorism, a short broad upturned nose, a wide mouth, a straight facial profile with incompetence of the lips, midline groove of tongue, and cleft palate. The patient also had severe anterior open bite, a distal step-type molar relationship, five congenitally missing teeth, and a supernumerary tooth. Lateral cephalometric analysis revealed a large anterior cranial base, a large maxilla and mandible, a large inferior face height, and skeletal Class I jaw relationship with a high mandibular plane angle and large gonial angle. The 3D CT image showed a large cranium, a long face height, and prominent skull sutures. The MR image showed a large tongue, midline groove of the tongue, and a small space between tongue and palate.

The human obesity gene map: the 2002 update

This is the ninth update of the human obesity gene map, incorporating published results through October 2002 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and various animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. For the first time, transgenic and knockout murine models exhibiting obesity as a phenotype are incorporated (N = 38). As of October 2002, 33 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and the causal genes or strong candidates have been identified for 23 of these syndromes. QTLs reported from animal models currently number 168; there are 68 human QTLs for obesity phenotypes from genome-wide scans. Additionally, significant linkage peaks with candidate genes have been identified in targeted studies. Seven genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 222 studies reporting positive associations with 71 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. More than 300 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.

Genotype/phenotype correlations of males affected by Simpson-Golabi-Behmel syndrome with GPC3 gene mutations: patient report and review of the literature

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked overgrowth syndrome with associated visceral and skeletal anomalies. Deletions or point mutations involving the glypican-3 (GPC3) gene at Xq26 are associated with a relatively milder form of this disorder (SGBS1). GPC3 encodes a putative extracellular proteoglycan, glypican-3, that is inferred to play an important role in growth control in embryonic mesodermal tissues in which it is selectively expressed. It appears to form a complex with insulin-like growth factor-II (IGF-II), and might thereby modulate IGF-II action. We reviewed the clinical findings of all published patients with SGBS1 with GPC3 mutations to confirm the clinical specificity for the SGBS1 phenotype. Moreover, we report on a new patient with a GPC3 deletion and IGF-II evaluation.

The human obesity gene map: the 2001 update

This report constitutes the eighth update of the human obesity gene map, incorporating published results up to the end of October 2001. Evidence from the rodent and human obesity cases caused by single-gene mutations, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) uncovered in human genome-wide scans and in crossbreeding experiments in various animal models, association and linkage studies with candidate genes and other markers is reviewed. The human cases of obesity related in some way to single-gene mutations in six different genes are incorporated. Twenty-five Mendelian disorders exhibiting obesity as one of their clinical manifestations have now been mapped. The number of different QTLs reported from animal models currently reaches 165. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 174 studies reporting positive associations with 58 candidate genes. Finally, 59 loci have been linked to obesity indicators in genomic scans and other linkage study designs. The obesity gene map depicted in Figure 1 reveals that putative loci affecting obesity-related phenotypes can be found on all chromosomes except chromosome Y. A total of 54 new loci have been added to the map in the past 12 months, and the number of genes, markers, and chromosomal regions that have been associated or linked with human obesity phenotypes is now above 250. Likewise, the number of negative studies, which are only partially reviewed here, is also on the rise.

Overgrowth of a mouse model of the Simpson-Golabi-Behmel syndrome is independent of IGF signaling

The type 1 Simpson-Golabi-Behmel overgrowth syndrome (SGBS1) is caused by loss-of-function mutations of the X-linked GPC3 gene encoding glypican-3, a cell-surface heparan sulfate proteoglycan that apparently plays a negative role in growth control by an unknown mechanism. Mice carrying a Gpc3 gene knockout exhibited several phenotypic features that resemble clinical hallmarks of SGBS1, including somatic overgrowth, renal dysplasia, accessory spleens, polydactyly, and placentomegaly. In Gpc3/DeltaH19 double mutants (lacking GPC3 and also carrying a deletion around the H19 gene region that causes bialellic expression of the closely linked Igf2 gene by imprint relaxation), the Gpc3-null phenotype was exacerbated, while additional SGBS1 features (omphalocele and skeletal defects) were manifested. However, results from a detailed comparative analysis of growth patterns in double mutants lacking GPC3 and also IGF2, IGF1, or the type 1 IGF receptor (IGF1R) provided conclusive genetic evidence inconsistent with the hypothesis that GPC3 acts as a growth suppressor by sequestering or downregulating an IGF ligand. Nevertheless, our data are compatible with a model positing that there is downstream convergence of the independent signaling pathways in which either IGFs or (indirectly) GPC3 participate.

GPC3 mutation analysis in a spectrum of patients with overgrowth expands the phenotype of Simpson-Golabi-Behmel syndrome

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked overgrowth syndrome caused by deletions in glypican 3 (GPC3). SGBS is characterized by pre- and postnatal overgrowth, a characteristic facial appearance, and a spectrum of congenital malformations which overlaps that of other overgrowth syndromes. We performed GPC3 deletion screening on 80 male patients with somatic overgrowth in the following categories: SGBS (n = 19), possible SGBS (n = 26), including families in which individuals had previously been diagnosed with other overgrowth syndromes, and Wiedemann-Beckwith syndrome (WBS) (n = 35). Using exon-specific PCR and Southern blot analysis, we identified seven GPC3 deletions. In most cases a clear X-linked family history was not present. In two cases, GPC3 deletions were identified in patients belonging to pedigrees published previously as other overgrowth syndromes: one with a diagnosis of Sotos syndrome and the other Perlman syndrome with nephroblastomatosis. A third patient developed hepatoblastoma, a tumor type not previously described in SGBS. No GPC3 deletions were identified among the WBS patients. Direct sequencing of all GPC3 exons in the remaining 13 SGBS patients without GPC3 deletions did not identify any further mutations, raising the possibility of alternative silencing mechanisms and/or other genes in the pathogenesis of SGBS. Our results validate the clinical specificity of the facial appearance, skeletal/hand anomalies, and supernumerary nipples in patients with GPC3 deletions. Our data also suggest that nephroblastomatosis and hepatoblastoma are included in the phenotypic spectrum of GPC3 deletions and SGBS, underscoring the importance of tumor surveillance in these children.

Simpson Golabi Behmel syndrome: progress toward understanding the molecular basis for overgrowth, malformation, and cancer predisposition

Simpson Golabi Behmel syndrome (SGBS) is a complex congenital overgrowth syndrome with features that include macroglossia, macrosomia, and renal and skeletal abnormalities as well as an increased risk of embryonal cancers. Most cases of SGBS appear to arise as a result of either deletions or point mutations within the glypican-3 (GPC3) gene at Xq26, one member of a multigene family encoding for at least six distinct glycosylphophatidylinositol-linked cell surface heparan sulfate proteoglycans. As a class of molecules, heparan sulfate proteoglycans have been found to play essential roles in development by modulating cellular responses to growth factors and morphogens. Specifically, mutations in both the murine GPC3 gene and the Drosophila glypican, dally, have been found to modify cellular responses to bone morphogenetic proteins, providing important clues to the molecular basis of SGBS in humans. Despite these advances, there remains a paucity of information about the natural history of SGBS and optimal medical management strategies, and whether select mutations influence the SGBS phenotype and risk of cancer. To this end, an International SGBS Registry has been created and is being maintained to improve the clinical care and understanding of the pathogenesis of SGBS. Using an integrated approach employing epidemiology, molecular genetic characterization of specific GPC3 mutations, and the use of model organisms should rapidly expand the understanding of this complex disorder.

The human obesity gene map: the 2000 update

This report constitutes the seventh update of the human obesity gene map incorporating published results up to the end of October 2000. Evidence from the rodent and human obesity cases caused by single-gene mutations, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci uncovered in human genome-wide scans and in cross-breeding experiments in various animal models, and association and linkage studies with candidate genes and other markers are reviewed. Forty-seven human cases of obesity caused by single-gene mutations in six different genes have been reported in the literature to date. Twenty-four Mendelian disorders exhibiting obesity as one of their clinical manifestations have now been mapped. The number of different quantitative trait loci reported from animal models currently reaches 115. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 130 studies reporting positive associations with 48 candidate genes. Finally, 59 loci have been linked to obesity indicators in genomic scans and other linkage study designs. The obesity gene map reveals that putative loci affecting obesity-related phenotypes can be found on all chromosomes except chromosome Y. A total of 54 new loci have been added to the map in the past 12 months and the number of genes, markers, and chromosomal regions that have been associated or linked with human obesity phenotypes is now above 250. Likewise, the number of negative studies, which are only partially reviewed here, is also on the rise.

The human obesity gene map: the 1999 update

This report constitutes the sixth update of the human obesity gene map incorporating published results up to the end of October 1999. Evidence from the rodent and human obesity cases caused by single gene mutations, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTL) uncovered in human genome-wide scans and in crossbreeding experiments with mouse, rat, pig and chicken models, association and linkage studies with candidate genes and other markers is reviewed. Twenty-five human cases of obesity can now be explained by variation in five genes. Twenty Mendelian disorders exhibiting obesity as one of their clinical manifestations have now been mapped. The number of different QTLs reported from animal models reaches now 98. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 89 reports of positive associations pertaining to 40 candidate genes. Finally, 44 loci have linked to obesity indicators in genomic scans and other linkage study designs. The obesity gene map depicted in Figure 1 reveals that putative loci affecting obesity-related phenotypes can be found on all autosomes, with chromosomes 14 and 21 showing each one locus only. The number of genes, markers, and chromosomal regions that have been associated or linked with human obesity phenotypes continues to increase and is now well above 200.