BSCL2 Research Articles

Progressive Myoclonus Epilepsy in Congenital Generalized Lipodystrophy type 2: Report of 3 cases and literature review

PurposeA small case series with a neurodegenerative disorder involving central nervous system and related to Seipin mutations was recently reported. Herein we describe clinical and EEG features of three patients presenting with Progressive Myoclonus Epilepsy (PME) and Congenital Generalized Lipodystrophy type 2 (CGL2) related to novel Seipin mutations. MethodsThe EEG-clinical picture was evaluated at epilepsy onset and in the follow-up period. The molecular analysis of BSCL2, Laforin and Malin genes was performed to patients and/or their parents by Denaturing High Performance Liquid Chromatography and automated nucleotide sequencing. Skin specimens collected from a patient were processed for histochemical and ultrastructural analysis. ResultsThe CGL2-PME syndrome co-segregated with two different BSCL2 genotypes: the homozygosity for c.782_783dupG involving exon 8 (two cases), or the compound heterozygosity for c.782_783dupG/c.828_829delAA (one case). Periodic-Acid Schiff positive osmiophilic material in the cytoplasm of fibrocytes and eccrine-gland cells were found in skin specimens. The lack of Lafora’s bodies in skin specimens and the molecular analysis excluding mutations in Laforin and Malin genes ruled out Lafora disease. ConclusionThe spectrum of CGL2 associated to BSCL2 gene mutations may include PMEs. Selected mutations in BSCL2 gene seem to be related to PMEs in patients with CGL2 phenotype.

Natural History of Congenital Generalized Lipodystrophy: A Nationwide Study From Turkey.

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by near-total lack of body fat. We aimed to study natural history and disease burden of various subtypes of CGL. We attempted to ascertain nearly all patients with CGL in Turkey. This was a nationwide study. Participants included 33 patients (22 families) with CGL and 30 healthy controls. We wanted to ascertain genotypes by sequencing of the known genes. Whole-body magnetic resonance imaging was used to investigate the extent of fat loss. Metabolic abnormalities and end-organ complications were measured on prospective follow-up. Analysis of the AGPAT2 gene revealed four previously reported and four novel mutations (CGL1; c.144C>A, c.667_705delinsCTGCG, c.268delC, and c.316+1G>T). Analysis of the BSCL2 gene revealed four different homozygous and one compound heterozygous possible disease-causing mutations (CGL2), including four novel mutations (c.280C>T, c.631delG, c.62A>T, and c.465-468delGACT). Two homozygous PTRF mutations (c.481-482insGTGA and c.259C>T) were identified (CGL4). Patients with CGL1 had preservation of adipose tissue in the palms, soles, scalp, and orbital region, and had relatively lower serum adiponectin levels as compared to CGL2 patients. CGL4 patients had myopathy and other distinct clinical features. All patients developed various metabolic abnormalities associated with insulin resistance. Hepatic involvement was more severe in CGL2. End-organ complications were observed at young ages. Two patients died at age 62 years from cardiovascular events. CGL patients from Turkey had both previously reported and novel mutations of the AGPAT2, BSCL2, and PTRF genes. Our study highlights the early onset of severe metabolic abnormalities and increased risk of end-organ complications in patients with CGL.

The relationship between adipocyte size and the transcript levels of SNAP23, BSCL2 and COPA genes in pigs

Breed-specific differences in fat tissue accumulation in the pig provide an opportunity to study the genetic background of this process. In the present study three pig breeds, differing in fatness, were analyzed in terms of the size of adipocytes derived from three tissues (subcutaneous, visceral and longissimus dorsi muscle) in relation to transcript levels of genes (SNAP23, BSCL2 and COPA), which encode proteins involved in lipid droplet formation. The analysis of adipocyte size revealed significant effects of breed and tissue and confirmed earlier reports that an elevated backfat thickness in some pig breeds is correlated with a larger adipocyte size. Variability in the transcript abundance of the studied genes among breeds and tissues was observed. We found a positive correlation between the abundance of the SNAP23 transcript and adipocyte diameter. The obtained results indicate that SNAP23 may be considered as an interesting candidate gene involved in adipose tissue growth in the pig.

Clinical and Molecular Characterization of BSCL2 Mutations in a Taiwanese Cohort with Hereditary Neuropathy.

BackgroundA small group of patients with inherited neuropathy that has been shown to be caused by mutations in the BSCL2 gene. However, little information is available about the role of BSCL2 mutations in inherited neuropathies in Taiwan.Methodology and Principal FindingsUtilizing targeted sequencing, 76 patients with molecularly unassigned Charcot-Marie-Tooth disease type 2 (CMT2) and 8 with distal hereditary motor neuropathy (dHMN), who were selected from 348 unrelated patients with inherited neuropathies, were screened for mutations in the coding regions of BSCL2. Two heterozygous BSCL2 mutations, p.S90L and p.R96H, were identified, of which the p.R96H mutation is novel. The p.S90L was identified in a pedigree with CMT2 while the p.R96H was identified in a patient with apparently sporadic dHMN. In vitro studies demonstrated that the p.R96H mutation results in a remarkably low seipin expression and reduced cell viability.ConclusionBSCL2 mutations account for a small number of patients with inherited neuropathies in Taiwan. The p.R96H mutation is associated with dHMN. This study expands the molecular spectrum of BSCL2 mutations and also emphasizes the pathogenic role of BSCL2 mutations in molecularly unassigned hereditary neuropathies.

Mutations in the BSCL2 gene cause congenital generalized lipodystrophy complicated by severe acute pancreatitis

Aims: DNA helicases play an important role in DNA replication, recombination and repair. We have previously shown a significant association of RecQ1 A159C polymorphic variant with a poor prognosis in patients with pancreatic cancer. The purpose of the current study is to explore the role of RecQ1 gene in cellular response to gemcitabine and in patient survival. Methods: RecQ1 protein expression was measured in tumor tissues of 67 patients with pancreatic cancer using immunohistochemistry and the protein expression level was analyzed in relation to overall survival. RecQ1 gene expression was knocked down by siRNA in pancreatic adenocarcinoma cell lines. Cell proliferation, apoptosis and cell cycle distribution as well as mRNA expression of DNA repair and cell cycle regulating genes were compared in cells treated with or without gemcitabine in vector control and RecQ1 knockdown cells.. Results: RecQ1 knockdown resulted in increased sensitivity (decreased proliferation and increased apoptosis) to gemcitabine treatment. RecQ1deficient cells had reduced S-Phase distribution in cells with or without gemcitabine treatment. RecQ1 knockdown down-regulated the expression of cell cycle check point signal transducers CHK1, CHK2 and RAD9, and many genes involved in S phase DNA replication and M phase regulation. Conclusions: These observations suggest that RecQ1 plays an important role in DNA repair and cell cycle regulation, which in turn affect the cellular sensitivity to gemcitabine.

The expression of SEIPIN in the mouse central nervous system.

Immunohistochemical staining was used to investigate the expression pattern of SEIPIN in the mouse central nervous system. SEIPIN was found to be present in a large number of areas, including the motor and somatosensory cortex, the thalamic nuclei, the hypothalamic nuclei, the mesencephalic nuclei, some cranial motor nuclei, the reticular formation of the brainstem, and the vestibular complex. Double labeling with NeuN antibody confirmed that SEIPIN-positive cells in some nuclei were neurons. Retrograde tracer injections into the spinal cord revealed that SEIPIN-positive neurons in the motor and somatosensory cortex and other movement related nuclei project to the mouse spinal cord. The present study found more nuclei positive for SEIPIN than shown using in situ hybridization and confirmed the presence of SEIPIN in neurons projecting to the spinal cord. The results of this study help to explain the clinical manifestations of patients with Berardinelli-Seip congenital lipodystrophy (Bscl2) gene mutations.

Génétique des lipodystrophies congénitales

Congenital lipodystrophies are heterogeneous genetic diseases, leading to the loss of adipose tissue. This loss of adipose tissue can be generalized or partial, thus defining different phenotypes. These lipodystrophies have a major metabolic impact, secondary to lipotoxicity. This lipotoxicity is responsible for insulin resistance, dyslipidemia and hepatic steatosis. The severity of the metabolic impact correlates with the severity of the loss of adipose tissue. Mutations in 15 predisposition genes are currently described; BSCL2 and AGPT2 genes are the major genes in the generalized forms. On the contrary, LMNA and PPARG gene mutations are recovered in partial lipodystrophies forms. These different genes encode for proteins involved in adipocyte physiology, altering adipocyte differentiation, triglycerides synthesis and lysis or playing a major role in the lipid droplet formation. Congenital lipodystrophies treatment is based on the management of metabolic comorbidities but recombinant leptin therapy appears to have promising results.These different points have been recently discussed during the 2015 Endocrine Society Congress, notably by S. O'Rahilly and are highlighted in this review.

AB143. Berardinelli-Seip congenital lipodystrophy and its diagnostic implications

Berardinelli-Seip congenital lipodystrophy (BSCLD) (OMIM#269700) is a rare autosomal recessive disorder characterized by marked paucity of adipose tissue, a muscular habitus, insulin resistance, hypertriglyceridemia and hepatic steatosis. It is an anabolic syndrome due to the deficiency of leptin, a lipid modulator, leading to the inappropriate mobilization of fat. Four types of BSCLD have been described based on the site of genetic mutation. Type 2 accounts for an earlier onset, more severe complications and intellectual disability. This is due to the lower leptin levels and the loss of functional seipin in type 2 BSCLD. We report the evolving phenotype of type 2 BSCLD in a boy clinically diagnosed at age 5 months and confirmed by molecular genetic study which revealed a pathogenic mutation in the BSCL2 gene: c.782dupG, p.lle262Hisfs*12homozygous. He is the firstborn of non-consanguineous parents with no significant family history. He has a muscular habitus with a distinct facies, hypertrichosis, absence of subcutaneous fat and hepatomegaly. Investigations revealed hypertriglyceridemia and insulin resistance. A conventional approach to management with dietary fat restriction successfully controlled his biochemical parameters, thus preventing catastrophic complications such as systemic arterial hypertension, heart failure and pancreatitis. Genetic counseling was conferred and prenatal testing recommended for future pregnancies. On follow-up, he had a muscular habitus with hepatomegaly and global developmental delay. Despite early correction of his biochemical parameters, an abdominal ultrasound revealed early onset fatty liver disease and an echocardiogram showed a thickened interventricular septum suggestive of early hypertrophic obstructive cardiomyopathy (HOCM). A fasting serum leptin done was low at 0.8 ng/mL (normal range, 2.0-5.6 ng/mL) confirming leptin deficiency. A leptin analog is now available as an adjunct to mollify the metabolic complications of BSCLD. However, it is yet to be available in developing nations and whether it is able to assuage progressive hepatic cholestasis and HOCM remains a field to venture. This report highlights the importance of early recognition and confirmation by molecular diagnosis to direct appropriate surveillance of complications. This also enables early genetic counseling and prenatal testing for future pregnancies. We describe the evolving phenotype, pertinent investigations and the conventional approach to the management of BSCLD.

Seipin is necessary for normal brain development and spermatogenesis in addition to adipogenesis

Seipin, encoded by BSCL2 gene, is a protein whose physiological functions remain unclear. Mutations of BSCL2 cause the most-severe form of congenital generalized lipodystrophy (CGL). BSCL2 mRNA is highly expressed in the brain and testis in addition to the adipose tissue in human, suggesting physiological roles of seipin in non-adipose tissues. Since we found BSCL2 mRNA expression pattern among organs in rat is similar to human while it is not highly expressed in mouse brain, we generated a Bscl2/seipin knockout (SKO) rat using the method with ENU (N-ethyl-N-nitrosourea) mutagenesis. SKO rats showed total lack of white adipose tissues including mechanical fat such as bone marrow and retro-orbital fats, while physiologically functional brown adipose tissue was preserved. Besides the lipodystrophic phenotypes, SKO rats showed impairment of spatial working memory with brain weight reduction and infertility with azoospermia. We confirmed reduction of brain volume and number of sperm in human patients with BSCL2 mutation. This is the first report demonstrating that seipin is necessary for normal brain development and spermatogenesis in addition to white adipose tissue development.

The role of continuous subcutaneous insulin infusion therapy in a case of Seip-Berardinelli congenital lipodystrophy

• A caucasian-male patient, currently with 21 years-old, was referred at 6-months-age because of “muscular phenotype” and liver function alterations. On examination, muscular appearance with minimal subcutaneous fat (Figure 1) and hepatosplenomegaly were identified. Laboratorial tests revealed abnormalities in cholestatic liver enzymes; glycemia was normal. Ultrasound exams documented diffuse liver steatosis and hypertrophic cardiomyopathy. The identification of heterozygous BSCL2 gene mutation (p.Pro65ArgfsX28 and p.Thr109AsnfsX5) established the diagnosis of SBCL type 2.

P.6.10 Phenotypic variability in a French family presenting with seipinopathy

Seipinopathies are a group of inherited diseases affecting upper and lower motor neurons due to mutations in the BSCL2 gene. Phenotype spectrum includes Silver syndrome, a form of hereditary spastic paraplegia (SPG17) and distal hereditary motor neuropathy type V. We report a French family carrying the N88S mutation in the BSCL2 gene. A 12-y-o girl complained of bilateral asymmetrical pes cavus. Physical exam revealed right hand motor deficit and amyotrophy. She also had asymmetrical leg amyotrophy and pyramidal signs. The electrophysiological exam showed axonal multifocal motor neuropathy with a distal predominance. Motor evoked potentials confirmed bilateral upper neuron impairment. At the age of 17, she was examined together with her father. He was a 46-y-o patient complaining of a rest tremor of the right hand associated with hand weakness. He had also noticed some wasting of the left hand muscles. His main history was a traumatism of the right peroneal tendon at the age of 6, later surgically treated by right ankle arthrodesis. Physical exam revealed left leg, hand and forearm amyotrophy. It was associated with akinesia and right arm rigidity. Reflexes were brisk at the lower limbs and bilateral Babinski sign was found. The EDX exam showed distal axonal multineuropathy with slight sensitive impairment. There was a moderate reduction of nerve conduction velocity in some nerves. l -Dopa was introduced, improving the Parkinson signs. Genetic testing revealed the presence of the N88S mutation in the BSCL2 gene in the proband and her father. BSCL2 mutations are associated with a wide clinical and electrophysiological spectrum and should be evoked in case of dHMN with pyramidal signs or early hand involvement. Mild demyelinating process could be associated and severity can be variable within the same family. Clinical diagnosis were made more difficult here due to the association with Parkinson symptoms, supposedly not linked to the BSCL2 gene mutation.

Deletion mutation in BSCL2 gene underlies congenital generalized lipodystrophy in a Pakistani family

BackgroundCongenital generalized lipodystrophy (CGL) also known as Berardinelli-Seip Congenital Lipodystrophy (BSCL) is a genetically heterogeneous disorder characterized by loss of adipose tissues, Acanthosis nigricans, diabetes mellitus, muscular hypertrophy, hepatomegaly and hypertriglyceridemia. There are four subclinical phenotypes of CGL (CGL1-4) and mutations in four genes AGPAT2, BSCL2, CAV1 and PTRF have been assigned to each type.MethodsThe study included clinical and molecular investigations of CGL disease in a consanguineous Pakistani family. For mutation screening all the coding exons including splice junctions of AGPAT2, BSCL2, CAV1 and PTRF genes were PCR amplified and sequenced directly using an automated DNA sequencer ABI3730.ResultsSequence analysis revealed a single base pair deletion mutation (c.636delC; p.Tyr213ThrfsX20) in exon 5 of BSCL2 gene causing a frame shift and premature termination codon.ConclusionMutation identified here in BSCL2 gene causing congenital generalized lipodystrophy is the first report in Pakistani population. The patients exhibited characteristic features of generalized lipodystrophy, Acanthosis nigricans, diabetes mellitus and hypertrophic cardiomyopathy.Virtual SlidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1913913076864247.

A new seipin-associated neurodegenerative syndrome

BackgroundSeipin/BSCL2 mutations can cause type 2 congenital generalised lipodystrophy (BSCL) or dominant motor neurone diseases. Type 2 BSCL is frequently associated with some degree of intellectual impairment, but not to...

Course of Atypical Manifestations of a Case of Charcot-Marie-Tooth Disease over 35 Years of Clinical Observation

Introduction: Atypical manifestations of peripheral neuropathy are not rare, challenging the differential diagnosis. In the past, the diagnosis of hereditary neuropathy was mainly based on the clinical and electromyographic (EMG) findings and, occasionally, biopsy. Nowadays, the genetic tests allow us to identify more than 40 different genes/loci associated with Charcot-Marie-Tooth (CMT) disease, although some subtypes are clinically indistinguishable. We have followed a patient with a clinical diagnosis of apparent sporadic and atypical CMT and recently diagnosed genetically as distal hereditary motor neuropathy, type V (dHMN-V). Case Report: Thirty-five years ago, a 16 years old patient complained muscular weakness and wasting at the hands small muscles. Sporadic fasciculations were observed whereas deep tendon reflexes and sensation were normal. EMG examination revealed neurogenic muscular denervation in the distribution of C7, C8 and T1 segments bilaterally. Muscular biopsy of the left Biceps Brachii showed rare atrophic fibers and some cellular atypia. The disease has undergone a clinical and EMG progression and diffusion over the years, involving the lower limbs and leading to a bilateral steppage. A more slight diffuse axonal motor neuropathy was also identified in the proband’s son and second cousin. The genetic study found a known missense mutation in BSCL2 gene related to a dHMN-V. Interestingly, there was a remarkable intra-familiar phenotypic variability, especially in the clinical onset and severity. Discussion: Atypical manifestations of hereditary neuropathies often overlap with other conditions. The present case highlights how a comprehensive clinical evaluation and a careful follow-up have led to a correct diagnosis even 35 years later and have allowed to identify other affected family members. The apparent lack of familiarity was probably due to the very soft presentation in the proband’s relatives. Although the genetic study was not available at that time, the first clinical diagnosis was not disavowed. The main differential diagnoses and a brief review of similar reported cases are discussed.

Diabetes lipoatrófica. Un reto terapéutico

Congenital generalised lipodystrophy is a rare autosomal recessive disorder characterised by a marked deficiency of adipose tissue and usually recognised at birth. This disorder is associated with early development of metabolic complications such as hypertriglyceridemia, hepatic steatosis, and insulin resistance. These complications ultimately lead to fatal events as a consequence of early atherosclerosis, lipoatrophic diabetes and hepatic cirrhosis. The authors report the case of a patient diagnosed, based on clinical and laboratory findings, in the first year of life. The established diagnosis was then confirmed by identifying a mutation in the BSCL2 gene. Because the hypertriglyceridemia and diabetes were refractory to treatment, the authors present this case in order to reflect on the best therapeutic management of this pathology.

A role for seipin in lipid droplet dynamics and inheritance in yeast

Malfunctions of processes involved in cellular lipid storage and mobilization induce the pathogenesis of prevalent human diseases such as obesity, type 2 diabetes and atherosclerosis. Lipid droplets are the main lipid storage depots for neutral lipids in eukaryotic cells, and as such fulfil an essential function to balance cellular lipid metabolism and energy homeostasis. Despite significant progress in identifying key metabolic enzymes involved in lipid storage and their regulation in various model organisms, some fundamental questions as to the biogenesis, subcellular distribution and inheritance of lipid droplets are as yet unsolved. In this study, we applied a set of imaging techniques such as high-resolution four-dimensional (4D) live-cell imaging, quantitative microscopy, transmission electron microscopy and electron tomography to gain insight into the spatio-temporal organization of lipid droplets during cellular growth in the yeast Saccharomyces cerevisiae. This analysis revealed a high level of organization of the subcellular positioning of lipid droplets in individual cells, their directed migration towards the cellular periphery and a coordinated transfer of a subpopulation of lipid droplets into daughter cells during cell division. Lipid droplets appear to remain associated with ER membranes during cellular growth independently of their size and subcellular localization. Deletion of FLD1, the functional orthologue of the human BSCL2 gene encoding seipin, leads to impaired dynamics of yeast lipid droplets and defective lipolysis, which might be due to aberrant ER structures in these mutants. Our data suggest a role for yeast seipin as a scaffolding protein that is required for the dynamics of a specific subdomain of the ER, and provide a new aspect for the interpretation of abnormal lipid droplets phenotypes in yeast mutants lacking seipin.

A Taiwanese Boy With Congenital Generalized Lipodystrophy Caused by Homozygous Ile262fs Mutation in the BSCL2 Gene

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disease that is characterized by a near-complete absence of adipose tissue from birth or early infancy. Mutations in the BSCL2 gene are known to result in CGL2, a more severe phenotype than CGL1, with earlier onset, more extensive fat loss and biochemical changes, more severe intellectual impairment, and more severe cardiomyopathy. We report a 3-month-old Taiwanese boy with initial presentation of a lack of subcutaneous fat, prominent musculature, generalized eruptive xanthomas, and extreme hypertriglyceridemia. Absence of mechanical adipose tissue in the orbits and scalp was revealed by head magnetic resonance imaging. Hepatomegaly was noticed, and histological examination of a liver biopsy specimen suggested severe hepatic steatosis and periportal necrosis. However, echocardiography indicated no sign of cardiomyopathy and he showed no distinct intellectual impairment that interfered with daily life. About 1 year later, abdominal computed tomography revealed enlargement of kidneys. He had a homozygous insertion of a nucleotide, 783insG (Ile262fs mutation), in exon 7 of the BSCL2 gene. We reviewed the genotype of CGL cases from Japan, India, China and Taiwan, and found that BSCL2 is a major causative gene for CGL in Asian.

SEIPIN S90L Mutation in an Italian family with CMT2/dHMN and pyramidal signs

Heterozygous mutations in the Berardinelli-Seip congenital lipodystrophy (BSCL2) gene have been associated with different clinical phenotypes including Silver syndrome/spastic paraplegia 17, distal hereditary motor neuropathy type V, and Charcot-Marie-Tooth disease type 2 (CMT2) with predominant hand involvement. We studied an Italian family with a CMT2 phenotype with pyramidal signs that had subclinical sensory involvement on sural nerve biopsy. Direct sequencing analysis of the BSCL2 gene in the three affected siblings revealed an S90L mutation. This report confirms the variability of clinical phenotypes associated with a BSCL2 Ser90Leu mutation and describes the first Italian family with this mutation.

PO32-FR-24 Heterozygous missense mutation in the BSCL2 gene in a Serbian family with distal hereditary motor neuropathy or silver syndrome

PO32-FR-24 Heterozygous missense mutation in the BSCL2 gene in a Serbian family with distal hereditary motor neuropathy or silver syndrome

Novel mutations of the BSCL2 and AGPAT2 genes in 10 families with Berardinelli–Seip congenital generalized lipodystrophy syndrome

Congenital generalized lipodystrophy, or Berardinelli-Seip syndrome, is a rare autosomal recessive disease caused by mutations in either the BSCL2 or AGPAT2 genes. This syndrome is characterized by an almost complete loss of adipose tissue usually diagnosed at birth or early infancy resulting in apparent muscle hypertrophy. Common clinical features are acanthosis nigricans, hepatomegaly with or without splenomegaly and high stature. Acromegaloid features, cardiomyopathy and mental retardation can also be present. We investigated 11 kindreds from different geographical areas of Brazil (northeast and southeast). All coding regions as well as flanking intronic regions of both genes were examined. Polymerase chain reaction (PCR) amplifications were performed using primers described previously and PCR products were sequenced directly. Four AGPAT2 and two BSCL2 families harboured the same set of mutations. BSCL2 gene mutations were found in the homozygous form in four kindreds (c.412C>T c.464T>C, c.518-519insA, IVS5-2A>G), and in two kindreds compound mutations were found (c.1363C>T, c.424A>G). In the other four families, one mutation of the AGPAT2 gene was found (IVS3-1G>C and c.299G>A). We have demonstrated four novel mutations of the BSCL2 and AGPAT2 genes responsible for Berardinelli-Seip syndrome and Brunzell syndrome (AGPAT2-related syndrome).