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

Simpson-Golabi-Behmel syndrome

The Simpson-Golabi-Behmel syndrome (SGBS; OMIM 312870) is an overgrowth/multiple congenital anomalies/dysplasia condition, inherited as an X-linked semi-dominant trait, with variable expressivity in males and reduced penetrance and expressivity in females. The clinical spectrum is broad, ranging from mild manifestations in both males and females to multiple malformations and neonatal death in the more severely affected cases. An increased risk of neoplasia is reported, requiring periodical surveillance. Intellectual development is normal in most cases. SGBS is caused by a loss-of-function mutation of the GPC3 gene, either deletions or point mutations, distributed all over the gene. Notably, GPC3 deletion/point mutations are not found in a significant proportion of clinically diagnosed SGBS cases. The protein product GPC3 is a glypican functioning as a receptor for Hh at the cell surface, involved in the Hh-Ptc-Smo signaling pathway, a regulator of cellular growth.

Clinical utility of periodic reinterpretation of CNVs of uncertain significance: an 8-year retrospective study

BACKGROUND

Array-CGH is the first-tier genetic test both in pre- and postnatal developmental disorders worldwide. Variants of uncertain significance (VUS) represent around 10~15% of reported copy number variants (CNVs). Even though VUS reanalysis has become usual in practice, no long-term study regarding CNV reinterpretation has been reported.

METHODS

This retrospective study examined 1641 CGH arrays performed over 8 years (2010-2017) to demonstrate the contribution of periodically re-analyzing CNVs of uncertain significance. CNVs were classified using AnnotSV on the one hand and manually curated on the other hand. The classification was based on the 2020 American College of Medical Genetics (ACMG) criteria.

RESULTS

Of the 1641 array-CGH analyzed, 259 (15.7%) showed at least one CNV initially reported as of uncertain significance. After reinterpretation, 106 of the 259 patients (40.9%) changed categories, and 12 of 259 (4.6%) had a VUS reclassified to likely pathogenic or pathogenic. Six were predisposing factors for neurodevelopmental disorder/autism spectrum disorder (ASD). CNV type (gain or loss) does not seem to impact the reclassification rate, unlike the length of the CNV: 75% of CNVs downgraded to benign or likely benign are less than 500 kb in size.

CONCLUSIONS

This study's high rate of reinterpretation suggests that CNV interpretation has rapidly evolved since 2010, thanks to the continuous enrichment of available databases. The reinterpreted CNV explained the phenotype for ten patients, leading to optimal genetic counseling. These findings suggest that CNVs should be reinterpreted at least every 2 years.

Frequently Expressed Glypican-3 As A Promising Novel Therapeutic Target for Osteosarcomas

Osteosarcoma (OS) is the most common bone malignancy without a reliable therapeutic target. Glypican-3 (GPC3) mutation and upregulation have been detected in multi-drug resistant OS, and anti-GPC3 immunotherapy can effectively suppress the growth of organoids. Further profiling of GPC3 mutations and expression patterns in OS is of clinical significance. To address these issues, fresh OS specimens were collected from 24 patients for cancer-targeted next-generation sequencing (NGS) and three-dimensional patient-derived organoid (PDO) culture. A tumor microarray was prepared using 37 archived OS specimens. Immunohistochemical (IHC) staining was performed on OS specimens and microarrays to profile GPC3 and CD133 expression as well as intratumoral distribution patterns. RT-PCR was conducted to semi-quantify GPC3 and CD133 expression levels in the OS tissues. Anti-GPC3 immunotherapy was performed on OS organoids with or without GPC3 expression and its efficacy was analyzed using multiple experimental approaches. No OS cases with GPC3 mutations were found, except for the positive control (OS-08). IHC staining revealed GPC3 expression in 73.77% (45/61) of OSs in weak (+; 29/45), moderate (++; 8/45), and strong (+++; 8/45) immunolabeling densities. The intratumoral distribution of GPC3-positive cells was variable in the focal (+; 10-30%; 8/45), partial (++; 31-70%; 22/45), and the most positive patterns (+++; > 71%; 15/45), which coincided with CD133 immunolabeling (P = 9.89×10^-10 ). The anti-GPC3 antibody efficiently inhibits Wnt/β-catenin signaling and induces apoptosis in GPC3-positive PDOs and PDXs, as opposed to GPC3-negative PDOs and PDXs. The high frequency of GPC3 and CD133 co-expression and the effectiveness of anti-wildtype GPC3-ab therapy in GPC3-positive OS models suggest that GPC3 is a novel prognostic parameter and a promising therapeutic target for osteosarcoma.

Precocious puberty in a case of Simpson-Golabi-Behmel syndrome with a de novo 240-kb deletion including GPC3

Here, we report a Japanese patient with Simpson-Golabi-Behmel syndrome involving a de novo 240-kb deletion including a part of GPC3. The patient showed pre- and postnatal macrosomia associated with coarse face, macrocephaly, supernumerary nipples, and cryptorchidism and characteristically presented with precocious puberty, mostly evaluated as advanced pubertal age of 15 years at the chronological age of 11.5 years.

Novel GPC3 Gene Mutation in Simpson-Golabi-Behmel Syndrome with Endocrine Anomalies: A Case Report

Simpson-Golabi-Behmel syndrome (SGBS) represents a rare X-linked recessive syndrome with prenatal and postnatal overgrowth, coarse facial features, congenital malformations, organomegaly and an increased risk of tumors. Mutations on the GPC3 gene, encoding the glypican-3 protein, have previously been shown to cause the disease. In this report, a 12-year-old Chinese boy was hospitalized in our institution for some clinical features of SGBS. His serum endocrine evaluation showed hormone level abnormalities, including high prolactin, high testosterone, high thyroid-stimulating hormone (TSH) levels, and low estradiol levels. Whole exome sequencing (WES) was performed in the patient for mutation analysis and a novel hemizygous mutation, c.185delT, p.(Leu62Cysfs*22), on the GPC3 gene, was identified. The mother was a heterozygous carrier. The SGBS patients might present with endocrine anomalies, which adds to the clinical heterogeneity of the disease. The novel GPC3 mutation c.185delT expands the mutational spectrum of the GPC3 gene.

A prenatal case of Simpson-Golabi-Behmel syndrome type 1 with a 0.26-Mb deletion fragment at Xq26.2 inherited from mother: Case report

RATIONALE

The purpose of this report was to explore how to manage the fetus of Simpson-Golabi-Behmel syndrome type 1 (SGBS1) and to provide a definite diagnosis to guide the following genetic counseling for the pregnancy.

PATIENT CONCERNS

A 24-year-old women, gravida 1, para 0, was 172 cm tall with weight 65 kg. She was referred to our center for counseling due to second-trimester ultrasound screening anomalies at 22 + 5 weeks of gestation age. Meanwhile the ultrasound examination indicated the overgrowth of the fetus. She and her husband were healthy and nonconsanguineous without family history.

DIAGNOSES

The karyotype and copy number variations sequencing (CNV-seq) combined with fetal ultrasound manifestation confirmed the diagnosis of SGBS1.

INTERVENTIONS

No treatment for the fetus.

OUTCOMES

Pregnancy was terminated.

LESSIONS

Once fetal overgrowth and other malformation are revealed in prenatal ultrasound, although without polyhydramnios and organomegaly, SGBS1 should be considered and further genetic testing such as CNV-seq and whole exon sequencing should be conducted to help clinicians provide a definite diagnosis to guide the following genetic counseling and the next pregnancy.

Hedgehog pathway modulation by glypican 3-conjugated heparan sulfate

Glypicans are a family of cell surface heparan sulfate proteoglycans that play critical roles in multiple cell signaling pathways. Glypicans consist of a globular core, an unstructured stalk modified with sulfated glycosaminoglycan chains, and a glycosylphosphatidylinositol anchor. Though these structural features are conserved, their individual contribution to glypican function remains obscure. Here, we investigate how glypican 3 (GPC3), which is mutated in Simpson-Golabi-Behmel tissue overgrowth syndrome, regulates Hedgehog signaling. We find that GPC3 is necessary for the Hedgehog response, surprisingly controlling a downstream signal transduction step. Purified GPC3 ectodomain rescues signaling when artificially recruited to the surface of GPC3-deficient cells but has dominant-negative activity when unattached. Strikingly, the purified stalk, modified with heparan sulfate but not chondroitin sulfate, is necessary and sufficient for activity. Our results demonstrate a novel function for GPC3-associated heparan sulfate and provide a framework for the functional dissection of glycosaminoglycans by in vivo biochemical complementation. This article has an associated First Person interview with the first author of the paper.

The function of Glypicans in the mammalian embryo

Glypicans are proteoglycans that are bound to the outer surface of the plasma membrane by a glycosylphosphatidylinositol anchor. The mammalian genome contains six members of the glypican family (GPC1 to GPC6). Although the degree of sequence homology within the family is rather low, the three-dimensional structure of these proteoglycans is highly conserved. Glypicans are predominantly expressed during embryonic development. Genetic and biochemical studies have shown that glypicans can stimulate or inhibit the signaling pathways triggered by Wnts, Hedgehogs, Fibroblast Growth Factors, and Bone Morphogenetic Proteins. The study of mutant mouse strains demonstrated that glypicans have important functions in the developmental morphogenesis of various organs. In addition, a role of glypicans in synapsis formation has been established. Notably, glypican loss-of-function mutations are the cause of three human inherited syndromes. Recent analysis of glypican compound mutant mice have demonstrated that members of this protein family display redundant functions during embryonic development.

Simpson-Golabi-Behmel syndrome in one of the Dichorionic-diamniotic twin: a case report and literature review

Background

Simpson-Golabi-Behmel syndrome (SGBS) is a rare X-linked overgrowth syndrome. The main clinical manifestations are overgrowth and multiple malformations.

Case presentation

A 38-year-old Chinese woman was pregnant with dichorionic-diamniotic (DCDA) twins after in-vitro fertilization. Series of ultrasound examinations indicated that the measurements (abdominal circumference and estimated foetal weight) of one twin were significantly greater than those of the other one. The genetic testing results of the larger baby indicated of Simpson-Golabi-Behmel syndrome.

Conclusion

SGBS is difficult to diagnose due to different clinical manifestations. Clinicians need to be more aware of typical SGBS’s clinical findings and choose genetic testing methods individually to improve its prenatal diagnosis.

In vitro and ex vivo models of adipocytes

Adipocytes are specialized cells with pleiotropic roles in physiology and pathology. Several types of fat cells with distinct metabolic properties coexist in various anatomically defined fat depots in mammals. White, beige, and brown adipocytes differ in their handling of lipids and thermogenic capacity, promoting differences in size and morphology. Moreover, adipocytes release lipids and proteins with paracrine and endocrine functions. The intrinsic properties of adipocytes pose specific challenges in culture. Mature adipocytes float in suspension culture due to high triacylglycerol content and are fragile. Moreover, a fully differentiated state, notably acquirement of the unilocular lipid droplet of white adipocyte, has so far not been reached in two-dimensional culture. Cultures of mouse and human-differentiated preadipocyte cell lines and primary cells have been established to mimic white, beige, and brown adipocytes. Here, we survey various models of differentiated preadipocyte cells and primary mature adipocyte survival describing main characteristics, culture conditions, advantages, and limitations. An important development is the advent of three-dimensional culture, notably of adipose spheroids that recapitulate in vivo adipocyte function and morphology in fat depots. Challenges for the future include isolation and culture of adipose-derived stem cells from different anatomic location in animal models and humans differing in sex, age, fat mass, and pathophysiological conditions. Further understanding of fat cell physiology and dysfunction will be achieved through genetic manipulation, notably CRISPR-mediated gene editing. Capturing adipocyte heterogeneity at the single-cell level within a single fat depot will be key to understanding diversities in cardiometabolic parameters among lean and obese individuals.

Syndromic Wilms tumor: a review of predisposing conditions, surveillance and treatment

Predisposing syndromes associated with an increased risk of Wilms tumor (WT) are responsible for 9–17% of all cases of the malignancy. Due to an earlier age at WT diagnosis and an increased incidence of bilateral and metachronous disease, management of syndromic WT warrants a distinct approach from that of non-syndromic WT. This review of English-language manuscripts about WT focuses on the most common syndromes, surveillance protocols and current treatment strategies. Highlighted syndromes include those associated with WT1, such as WAGR (Wilms-Aniridia-Genitourinary-mental Retardation), Denys-Drash syndrome (DDS), and Frasier syndrome, 11p15 defects, such as Beckwith-Wiedemann syndrome (BWS), among others. General surveillance guidelines include screening renal or abdominal ultrasound every 3–4 months until the age of 5 or 7, depending on the syndrome. Further, some of the predisposing conditions also increase the risk of other malignancies, such as gonadoblastoma and hepatoblastoma. With promising results for nephron-sparing surgery in bilateral non-syndromic WT, there are increasing reports and recommendations to pursue nephron-sparing for these patients who are at greater risk of bilateral, metachronous lesions. In addition to the loss of renal parenchyma from malignancy, many patients are at risk of developing renal insufficiency as part of their syndrome. Although there may be some increase in the complication rate, recurrence free survival seems equivalent. Some conditions require specialized approaches to adjuvant therapy, as their syndrome may make them especially susceptible to side effects.

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.

Whole exome sequencing aids the diagnosis of Simpson-Golabi-Behmel syndrome in two male fetuses

Objective

To diagnose and explore the genetic aetiology of Simpson–Golabi–Behmel syndrome type 1 (SGBS1) in two male fetuses.

Methods

Prenatal ultrasound scans and further genetic analysis using karyotype analysis, chromosomal microarray analysis, whole exome sequencing (WES) and Sanger sequencing were conducted.

Results

Prenatal ultrasound scans of two fetuses showed multiple congenital anomalies and hydramnios. Subsequent to termination of the pregnancies, a novel nonsense variant (c.892G>T, p.E298*) in the glypican 3 (GPC3) gene of the two fetuses was identified by WES and further confirmed by Sanger sequencing. The two fetuses were diagnosed with SGBS1. The mother was heterozygous for the c.892G>T variant.

Conclusion

This study describes the prenatal sonographic features of SGBS1, emphasizes the role of WES in the diagnosis of SGBS1 and expands the known mutation spectrum of the GPC3 gene.

Overgrowth syndromes - clinical and molecular aspects and tumour risk

Overgrowth syndromes are a heterogeneous group of rare disorders characterized by generalized or segmental excessive growth commonly associated with additional features, such as visceromegaly, macrocephaly and a large range of various symptoms. These syndromes are caused by either genetic or epigenetic anomalies affecting factors involved in cell proliferation and/or the regulation of epigenetic markers. Some of these conditions are associated with neurological anomalies, such as cognitive impairment or autism. Overgrowth syndromes are frequently associated with an increased risk of cancer (embryonic tumours during infancy or carcinomas during adulthood), but with a highly variable prevalence. Given this risk, syndrome-specific tumour screening protocols have recently been established for some of these conditions. Certain specific clinical traits make it possible to discriminate between different syndromes and orient molecular explorations to determine which molecular tests to conduct, despite the syndromes having overlapping clinical features. Recent advances in molecular techniques using next-generation sequencing approaches have increased the number of patients with an identified molecular defect (especially patients with segmental overgrowth). This Review discusses the clinical and molecular diagnosis, tumour risk and recommendations for tumour screening for the most prevalent generalized and segmental overgrowth syndromes.

Immunotherapeutic Targeting of GPC3 in Pediatric Solid Embryonal Tumors

Glypican 3 (GPC3) is a heparan sulfate proteoglycan and cell surface oncofetal protein which is highly expressed on a variety of pediatric solid embryonal tumors including the majority of hepatoblastomas, Wilms tumors, rhabdoid tumors, certain germ cell tumor subtypes, and a minority of rhabdomyosarcomas. Via both its core protein and heparan sulfate side chains, GPC3 activates the canonical Wnt/β-catenin pathway, which is frequently overexpressed in these malignancies. Loss of function mutations in GPC3 lead to Simpson-Golabi-Behmel Syndrome, an X-linked overgrowth condition with a predisposition to GPC3-expressing cancers including hepatoblastoma and Wilms tumor. There are several immunotherapeutic approaches to targeting GPC3, including vaccines, monoclonal antibodies, antibody-drug conjugates, bispecific antibodies, cytolytic T lymphocytes, and CAR T cells. These therapies offer a potentially novel means to target these pediatric solid embryonal tumors. A key pediatric-specific consideration of GPC3-targeted immunotherapeutics is that GPC3 can be physiologically expressed in normal tissues during the first year of life, particularly in the liver and kidney. In summary, this article reviews the current evidence for targeting childhood cancers with GPC3-directed immunotherapies.

CUGC for Simpson-Golabi-Behmel syndrome (SGBS)

NAME OF THE DISEASE (SYNONYMS)

Simpson-Golabi-Behmel syndrome (SGBS). OMIM# OF THE DISEASE: 312870.

NAME OF THE ANALYSED GENES OR DNA/CHROMOSOME SEGMENTS

GPC3. OMIM# OF THE GENE(S): 300037. Review of the analytical and clinical validity as well as of the clinical utility of DNA-based testing for mutations in the GPC3 gene(s) in ⊠ diagnostic, ☐ predictive and ⊠ prenatal settings and for ⊠ risk assessment in relatives.

Synchronous occurrence of multiple distinct jaw lesions in Simpson-Golabi-Behmel Syndrome: A case report

Simpson-Golabi-Behmel Syndrome (SGBS) is an X-linked overgrowth syndrome characterized by pre- and post-natal overgrowth, typical facial appearance and multiple visceral, skeletal, and neurological anomalies. There is only few information in the current literature, on clinical and particularly dentofacial findings due to recent identification of the syndrome and its clinical overlap with other overgrowth syndromes. The aim of this case report is to present dentofacial findings in a 16-year-old boy who had been diagnosed with SGBS. Following comprehensive clinical, radiographic and histopathological examinations, six pathologically distinct lesions including odontogenic keratocyst, ameloblastoma, lateral periodontal cyst, dentigerous cyst and mucous retention cyst in both mandible and maxilla were identified. The clinical report is followed by a discussion aimed to clarify unique features of this condition and how practitioners should consider similar cases.