PIK3CA mutations in lipomatosis of nerve with or without nerve territory overgrowth.

Lipomatosis of nerve is a rare malformation characterized by a fibrolipomatous proliferation within peripheral nerve. Lipomatosis of nerve most frequently involves the median nerve, and manifests clinically as a compressive neuropathy. However, 30-60% of cases are associated with tissue overgrowth within the affected nerve's territory (e.g., macrodactyly for lipomatosis of nerve in the distal median nerve). Somatic activating PIK3CA mutations have been identified in peripheral nerve from patients with lipomatosis of nerve with type I macrodactyly, which is now classified as a PIK3CA-related overgrowth spectrum disorder. However, the PIK3CA mutation status of histologically confirmed lipomatosis of nerve, including cases involving proximal nerves, and cases without territory overgrowth, has not been determined. Fourteen histologically confirmed cases of lipomatosis of nerve involving the median (N = 6), brachial plexus (N = 1), ulnar (N = 3), plantar (N = 2), sciatic and superficial peroneal nerves (N = 1 each) were included. Ten cases had nerve territory overgrowth, ranging from macrodactyly to hemihypertrophy; and four cases had no territory overgrowth. Exome sequencing revealed "hotspot" activating PIK3CA missense mutations in 6/7 cases. Droplet digital polymerase chain reaction for the five most common PIK3CA mutations (p.H1047R, p.H1047L, p.E545K, p.E542K, and p.C420R) confirmed the exome results and identified an additional six cases with mutations (12/14 total). PIK3CA mutations were found in 8/10 cases with territory overgrowth (N = 7 p.H1047R and N = 1 p.E545K), including two proximal nerve cases with extremity overgrowth, and 4/4 cases without territory overgrowth (p.H1047R and p.H1047L, N = 2 each). The variant allele frequency of PIK3CA mutations (6-32%) did not correlate with the overgrowth phenotype. Three intraneural lipomas had no detected PIK3CA mutations. As PIK3CA mutations are frequent events in lipomatosis of nerve, irrespective of anatomic site or territory overgrowth, we propose that all phenotypic variants of this entity be classified within the PIK3CA-related overgrowth spectrum and termed "PIK3CA-related lipomatosis of nerve".

Somatic PIK3CA mutations are present in multiple tissues of facial infiltrating lipomatosis.

BackgroundFacial infiltrating lipomatosis (FIL) is a congenital disorder that causes overgrowth of one side of the face. The purpose of this study was to determine whether PIK3CA mutations are present in tissues outside of the subcutaneous adipose.MethodsFIL tissues from three patients were dissected to enrich for cells from skin, subcutaneous tissue, orbicularis oris muscle, buccal fat, zygomatic bone, and mucosal neuroma. Endothelial cells within the affected tissue also were enriched using CD31 microbeads. Laser capture microdissection on formalin-fixed paraffin-embedded histologic sections was performed to collect specific cell types. DNA was extracted from each tissue and cell type, and measured for the abundance of mutant PIK3CA alleles using droplet digital PCR.ResultsWe detected mutant PIK3CA alleles in every tissue and cell type tested from each overgrown face; frequencies ranged from 1.5 to 53%. There were fewer mutant endothelial cells compared with nonendothelial cells, and the stromal cell compartment had the highest frequency of mutant cells in each tissue.ConclusionsPIK3CA mutations are not restricted to a single tissue or cell type in FIL. Overgrowth in this condition is likely due to the mutation arising in a cell that contributes to several different facial structures during embryogenesis.

Mutations in EFL1, an SBDS partner, are associated with infantile pancytopenia, exocrine pancreatic insufficiency and skeletal anomalies in aShwachman-Diamond like syndrome.

BACKGROUND: For the final step of the maturation of the ribosome, the nascent 40S and 60S subunits are exported from the nucleus to the cell cytoplasm. To prevent premature association of these ribosomal subunits, eukaryotic initiation factor 6 (eIF6) binds the 60S subunit within the nucleus. Its release in the cytoplasm requires the interaction of EFL1 and SDBS proteins. In Shwachman-Diamond syndrome (SDS), a defective SDBS protein prevents eIF6 eviction, inhibiting its recycle to the nucleus and subsequent formation of the active 80S ribosome. OBJECTIVE: This study aims to identify the molecular basis of an SDS-like disease, manifested by pancytopenia, exocrine pancreatic insufficiency and skeletal abnormalities in six patients from three unrelated families. METHODS: Whole exome analysis was used for mutation identification. Fluorescence microscopy studies assessed the localisation of Tif6-GFP, the yeast eIF6 homologue, in yeast WT and mutant cells. Human and yeast EFL1 proteins, WT and mutants, were expressed in Saccharomyces cerevisiae BCY123 strain, and circular dichroism and small-angle X-ray scattering were used to assess the folding and flexibility of these proteins. Green malachite colorimetric assay was performed to determine the GTPase activity of WT and Efl1 mutants. RESULTS: Four patients were homozygous for p.R1095Q variant and two patients were homozygous for p.M882K variant in EFL1. Residue R1095 and M882 are conserved across species. Neither the GTPase activity of the mutant proteins nor its activation by the SDBD protein or the 60S ribosomal subunit were affected. Complementation of efl1Δ yeast cells with the EFL1 mutants rescued the slow growth phenotype. Nonetheless, Tif6-GFP was relocalised to the cytoplasm in mutant yeast cells in contrast to its nuclear localisation in WT cells. CONCLUSIONS: Mutations in EFL1 clinically manifest as SDS-like phenotype. Similar to the molecular pathology of SDS, mutant EFL1 proteins do not promote the release of cytoplasmic Tif6 from the 60S subunit, likely preventing the formation of mature ribosomes.

Loss of mitochondrial SDHB expression: what is its role in diffuse thyroid lipomatosis?

Diffuse lipomatosis of the thyroid gland is a very rare disease, characterized by extensive infiltration of thyroid parenchyma by mature adipose tissue, usually not accompanied by amyloid fibrils deposition. The pathophysiology of adipose tissue infiltration in the thyroid gland remains unknown. We report a clinical case of a diffuse thyroid lipomatosis, whose immunohistochemical study of succinate dehydrogenase - subunit B (SDHB) revealed loss of expression of this protein in the follicular or adipose cells. We detected the presence of a recently described SDHB gene large deletion. Loss of mitochondrial SDHB expression may have a key role in understanding the pathophysiology of thyrolipomatosis, by regulating status of lipid metabolism.

Somatic mosaicism for the p.His1047Arg mutation in PIK3CA in a girl with mesenteric lipomatosis.

We describe a patient who presented with a localized growth of mature fat tissue, which was surgically removed. MRI imaging identified diffuse increase in visceral adipose tissue. Targeted deep sequencing of the resected tissue uncovered a p.H1047R variant in PIK3CA, which was absent in blood. This report expands the phenotypic spectrum of mosaic PIK3CA mutations.

The histopathology of PRSS1 hereditary pancreatitis.

Hereditary pancreatitis is an autosomal dominant disorder with 80% penetrance and variable expressivity. The vast majority of cases have been linked to mutations within the cationic trypsinogen gene, also referred to as serine protease 1 (PRSS1). Other than inheritance, PRSS1 pancreatitis has been considered clinically and pathologically indistinguishable from other etiologies of chronic pancreatitis. However, to date, the histologic findings of PRSS1 pancreatitis have not been well described. We, therefore, collected pancreatic specimens from 10 PRSS1 patients of various ages and examined their clinicopathologic features. Patients at the time of resection ranged in age from 9 to 66 years (median, 29 y), with a slight female predominance (60%). All patients reported a history of intermittent abdominal pain, with an age of onset ranging from infancy to 21 years of age. Examination of the gross and microscopic findings suggested a sequential pattern of changes with increasing patient age. In pediatric patients (n=4), although in most cases the pancreas was grossly normal, there was microscopic variation in lobular size and shape. Although the central portions of the pancreas displayed parenchymal loss accompanied by loose perilobular and interlobular fibrosis, the periphery was remarkable for replacement by mature adipose tissue. These changes were more developed in younger adults (n=2), in whom fatty replacement seemed to extend from the periphery to the central portions of the pancreas. With older patients (n=4), the pancreas showed marked atrophy and extensive replacement by mature adipose tissue with scattered islets of Langerhans and rare acinar epithelium concentrated near the main pancreatic duct. In summary, PRSS1 hereditary pancreatitis is characterized by progressive lipomatous atrophy of the pancreas.

Guanine nucleotide exchange in the ribosomal GTPase EFL1 is modulated by the protein mutated in the Shwachman-Diamond syndrome.

Ribosome biogenesis in eukaryotes is a complex process that requires the participation of several accessory proteins that are not part of the mature particle. Efl1 is a yeast GTPase required for the cytoplasmic maturation of the 60S ribosomal subunit. Together with Sdo1, the yeast ortholog of the protein mutated in the Shwachman-Diamond Syndrome (SBDS), Efl1 releases the anti-association factor Tif6 from the surface of the 60S subunit allowing the assembly of mature ribosomes. We characterized the structural content and folding stability of the Saccharomyces cerevisiae and human EFL1 GTPases, as well as their enzymatic properties alone and in the presence of Sdo1 and SBDS, respectively. The human and S. cerevisiae EFL1 GTPases are composed of a mixture of α-helices and ß-sheets. Despite being orthologs, the yeast protein elicited a non-two state thermal unfolding behavior while the human EFL1 was highly resistant to thermal denaturation. Steady-state kinetic analyses indicated slow GTP hydrolysis for both EFL1 GTPases, with kcat values of 0.4 and 0.3min(-1) and Km for GTP of 110 and 180µM respectively. In the presence of the effector proteins, their kcat values remained unaltered while the Km decreased twofold suggesting that Sdo1 and SBDS act as nucleotide exchange factors.

Pluripotent stem cell models of Shwachman-Diamond syndrome reveal a common mechanism for pancreatic and hematopoietic dysfunction.

Shwachman-Diamond syndrome (SDS), a rare autosomal-recessive disorder characterized by exocrine pancreatic insufficiency and hematopoietic dysfunction, is caused by mutations in the Shwachman-Bodian-Diamond syndrome (SBDS) gene. We created human pluripotent stem cell models of SDS through knockdown of SBDS in human embryonic stem cells (hESCs) and generation of induced pluripotent stem cell (iPSC) lines from two patients with SDS. SBDS-deficient hESCs and iPSCs manifest deficits in exocrine pancreatic and hematopoietic differentiation in vitro, enhanced apoptosis, and elevated protease levels in culture supernatants, which could be reversed by restoring SBDS protein expression through transgene rescue or by supplementing culture media with protease inhibitors. Protease-mediated autodigestion provides a mechanistic link between the pancreatic and hematopoietic phenotypes in SDS, highlighting the utility of hESCs and iPSCs in obtaining novel insights into human disease.

[Status of the antioxidant enzyme system in benign symmetrical lipomatosis and changes in it from the use of antioxidant therapy]. / Sostoianie antiokislitel'noi fermentnoi sistemy pri dobrokachestvennom simmetrichnom lipomatoze i ee izmeneniia pod vliianiem antioksidantnoi terapii.

Activity of the antioxidation enzymatic system, involving evaluation of glutathione-reductase, -peroxidase and -S-transferase as well as glucose-6-phosphate dehydrogenase activities, was studied in blood plasma, leukocytes, lymphocytes and erythrocytes of patients with benign symmetric lipomatosis. Elevation in the rate of lipid peroxidation induced the antioxidation enzymatic system and caused a imbalance of its individual units. Intensive antioxidation therapy using "Aevit" allowed correction of the imbalance observed in the enzymatic activity.

Multiple symmetric lipomatosis: abnormalities in complex IV and multiple deletions in mitochondrial DNA.

Multiple symmetric lipomatosis (MSL) is a rare disorder of middle life characterized by large nonencapsulated lipomas distributed around the neck, shoulders, and other axial regions. Neurologic involvement, particularly peripheral neuropathy, is frequent. The pathogenesis of the syndrome is still unknown, but ragged-red fibers are occasionally present in muscle of affected patients, suggesting a mitochondrial abnormality. We studied 11 unrelated patients with MSL by means of neurophysiology, muscle morphology, muscle biochemistry, Southern blot, and PCR analysis of mitochondrial DNA. All patients were men aged 41 to 63 years. Clinical or electrophysiologic signs of a sensorimotor polyneuropathy were present in nine patients, eight of whom had a history of alcoholism. In muscle biopsy specimens, the most prominent feature was pathologic subsarcolemmal aggregates of mitochondria. Biochemical analysis of respiratory chain enzymes revealed a moderate but significant decrease of cytochrome c oxidase activity as compared with age-matched controls. In one patient, Southern blot analysis showed multiple deletions of mitochondrial DNA. We conclude that mitochondrial dysfunction is common in MSL and may be based on identifiable defects in the mitochondrial genome.

Lipoprotein metabolism in patients with elevated lipoprotein-lipase activity in adipose tissue.

We have evaluated the relationships between adipose tissue lipoprotein-lipase activity (AT-LPL) or post-heparin plasma lipolytic activity (PHLA) and the composition of circulating lipoproteins in 7 patients with multiple symmetric lipomatosis (MSL). In addition we have investigated the behaviour of serum triglycerides after an oral fat load (1 g triglycerides/kg body weight) in 5 MSL patients and in 5 age and sex matched controls. We found significantly higher values of HDL, HDL2 and HDL3 cholesterol in MSL patients than in controls. Moreover, HDL2/HDL3 cholesterol ratio was higher in MSL patients than in controls, which indicate a predominant increase in HDL2 subfraction. The mean values of AT-LPL in lipomatous tissue was significantly higher than in control tissue. A positive statistically significant correlation was found between AT-LPL activity and HDL, HDL2 and HDL3 cholesterol values. After the fat load the maximal increments of serum triglyceride levels and the triglyceride areas over 8 and 12 h are lower in MSL patients than in controls; there was an inverse, statistically significant correlation between the total PHLA or the extrahepatic PHLA values and the triglyceride areas after lipid load. We conclude that MSL represents a useful naturally occurring model for the study of the role of AT-LPL in the metabolism of triglyceride-rich lipoproteins and in the clearance of lipoproteins in the post-prandial phase.

Adenylate cyclase of multiple lipomata. Regional differences in adrenaline-responsiveness.

Multiple symmetric lipomatosis has been proposed to be associated with impaired catecholamine-responsiveness of hypertrophic adipose tissue at the level of beta-adrenergic receptors or adenylate cyclase respectively. We have studied the regulation of the adenylate cyclase by guanine nucleotides and adrenaline in 5 subjects suffering from multiple encapsulated lipomata. In the presence of GTP (0.1 mmol/l) basal adenylate cyclase activity averaged 0.5 +/- 0.3 nmol cAMP/mg protein/10 minutes in normal adipose tissue and 1.0 +/- 0.4 nmol cAMP/mg protein/10 minutes in hypertrophic adipose tissue respectively. The synthetic GTP-analogue GMP(PNP) (0.1 mmol/l) increased non-stimulated activity by about 100% in both tissues. Adrenaline (1 mumol/l-1 mmol/l) caused a dose-dependent increase of enzymic activity in both tissues which had a maximum of 130% above basal levels in the presence of GTP and of 300% in the presence of GMP(PNP) respectively. In one of the six subjects suffering from gluteal lipomata normal adipose tissue was obtained from the gluteal as well as the abdominal region on two occasions. Maximally effective concentrations of adrenaline (1 mmol/l) induced a 3-fold increase of enzymic activity in abdominal membranes compared with about a 1.7- and 1.75-fold increase in normal and lipomatous tissue from the gluteal region. The results show that encapsulated lipomata contain a normally reactive adenylate cyclase system.

Molecular biology of metabolic disease: defects in the regulation of enzymic activity.

The Jacob-Monod model for the regulation of enzymic activity has been used in the analysis of some types of metabolic disease. Three lesions have been considered: (1) loss of allosteric inhibition of phosphofructokinase by citrate in the condition of lipomatosis; (2) failure of covalent modification of triglyceride lipase from inactive to active forms in the condition of triglyceride storage disease, and (3) failure of repression of HMG-CoA reductase by a mutant low-density liprotein in a new variant-of familial hypercholesterolaemia. Defects in enzymic regulation are contrasted with catalytic defects (the inborn errors); the major difference being an accumulation of a normal metabolic end-product of an unregulated pathway, rather than accumulation of an unusual intermediary metabolite as in the inborn errors.

[Clinical and biochemical study of 2 cases of lipomatosis]. / Etude clinique et biochimique de deux cas de lipomatose.

The authors report two cases of lipomatosis. Biochemical study of lipomas revealed, in comparison with normal adipose tissue:--an increase in lipasic lipoprotein activity;--a decrease in lipasic triglyceride activity. These changes could be in part implicated in the mechanisms of fatty accumulation within the lipomas, without explaining the topography and encapsulation.

Lipoprotein lipase and hormone-sensitive lipase activities in human subcutaneous lipomas: comparison with normal subcutaneous adipose tissue.

1. Lipoprotein lipase activity and hormone-sensitive lipase activity were investigated in subcutaneous lipomas removed from two patients and compared with the enzyme activities in subcutaneous adipose tissue from two normal subjects. 2. Confirmation was obtained of the presence of lipoprotein lipase activity in lipomas with an activity fifteen to forty-five times that in the two control samples. 3. Hormone-sensitive lipase activity was demonstrated in lipomas under basal conditions of assay as well as in the presence of adrenaline plus theophylline. However, compared with the non-lipomatous fat samples, these activities were lower, as was the magnitude of the lipolytic response to adrenaline plus theophylline. 4. The significance of these measurements of enzyme activity and their role in the pathogenesis of lipomas are briefly discussed.

Errors in metabolic regulation. A common group of metabolic disorders.

It is postulated that errors in metabolic regulation occur when aminoacid subsitutions or conformational changes occur at allosteric sites on proteins. The cell thus contains its full complement of enzymes, carrier proteins, and receptors, but these proteins do not respond normally to microenvironmental agents such as hormones or activator or inhibitor metabolites. Regulatory errors differ from the classical inborn errors in a number of respects: they can be acquired as well as inherited, when due to defects at allosteric inhibitory sites they lead to loss of regulation of metabolic pathways with oversynthesis of metabolic products without gross accumulation of abnormal intermediates, and they can be treated, in principle, by enzyme inhibitors rather than by enzyme replacement, as for inborn errors.