LPIN2 Gene Research Articles

Majeed syndrome: first description in a patient of central-European ancestry.

We present the first case of a Majeed syndrome in a girl of central-European ancestry. : Patient's medical records were reviewed. A NGS panel for autoinflammatory diseases was performed and the mutation was confirmed by Sanger analysis. Freshly isolated monocytes were activated with LPS +/- ATP. The concentration of inflammatory cytokines was assessed in monocytes supernatants. A 2-year-old girl presented with pain in the lower limbs, increase of acute phase reactants and persistent microcytic anaemia. The MRI showed bilateral STIR hyper-intensity of the spongy osseous tissue of femur, tibia, radius, ulna, and astragalus. Bone marrow analysis revealed increased trilinear cellularity with signs of dyserythropoietic anaemia. NGS panel detected the presence of two novel compound heterozygous mutations in the LPIN2 gene, confirmed by Sanger analysis. Treatment with anakinra was started with a prompt resolution of the clinical picture. Increased kinetics and concentration of IL-1β was observed in the patient's monocytes compared with healthy controls, with a marked drop following the start of therapy. About six months after the start of the therapy, resolution of MRI findings, microcytic anaemia and dyserythropoiesis at bone marrow aspirate was observed. We describe the first case of Majeed syndrome in a patient of central-European ancestry. The functional test on circulating monocytes before and after therapy with anakinra confirmed pathogenicity of the mutation and the role of LPIN2 in the NLRP3 inflammasome activation. Anti-IL1 agents were effective, leading not only to the resolution of bone lesion but also to an improvement of dyserythropoiesis.

Genome-wide analysis study of gestational diabetes mellitus and related pathogenic factors in a Chinese Han population

BackgroundGestational diabetes mellitus (GDM) affects the metabolism of both the mother and fetus during and after pregnancy. Genetic factors are important in the pathogenesis of GDM, and associations vary by ethnicity. However, related studies about the relationship between the susceptibility genes and glucose traits remain limited in China. This study aimed to identify genes associated with GDM susceptibility in Chinese Han women and validate those findings using clinical data during pregnancy and postpartum period.MethodsA genome-wide association study (GWAS) of 398 Chinese Han women (199 each with and without GDM) was conducted and associations between single nucleotide polymorphisms (SNPs) and glucose metabolism were identified by searching public databases. Relationships between filtered differential SNPs and glucose metabolism were verified using clinical data during pregnancy. The GDM group were followed up postpartum to evaluate the progression of glucose metabolism.ResultsWe identified five novel SNPs with genome-wide significant associations with GDM: rs62069863 in TRPV3 gene and rs2232016 in PRMT6 gene were positive correlated with 1 h plasma glucose (1hPG) and 2 h plasma glucose (2hPG), rs1112718 in HHEX/EXOC6 gene and rs10460009 in LPIN2 gene were positive associated with fasting plasma glucose, 1hPG and 2hPG, rs927316 in GLIS3 gene was negative correlated with 2hPG. Of the 166 GDM women followed up postpartum, rs62069863 in TRPV3 gene was positively associated with fasting insulin, homoeostasis model assessment of insulin resistance.ConclusionsThe variants of rs62069863 in TRPV3 gene, rs2232016 in PRMT6 gene, rs1112718 in HHEX/EXOC6 gene, rs927316 in GLIS3 gene, and rs10460009 in LPIN2 gene were newly-identified susceptibility loci for GDM in the Chinese Han population. TRPV3 was associated with worse insulin resistance postpartum.Trial registrationThis study was registered in the Chinese Clinical Trial Registry. Trial registration number: ChiCTR2100043762. Date of first registration: 28/02/2021.

Clinical and genetic analysis of a child with Majeed syndrome

To explore the clinical feature, diagnosis and phenotype of Majeed syndrome. Clinical manifestation, diagnostic process, imaging feature and genetic testing of an ethnic Han Chinese patient with Majeed syndrome were reviewed. The patient, a 3-year-9-month-old boy, had featured psychomotor retardation and developed bone pain from 8 month on. The child had tenderness of the lower limbs and presented with repeatedly joint swelling and pain accompanied by fever. Physical signs included limb muscle weakening, slightly decreased muscle tone, reduced muscle volume and positive Gower sign. High-throughput sequencing revealed that the child has carried compound heterozygous variants of the LPIN2 gene, including c.1966A>G and c.2534delG. MRI showed multiple lesions in bilateral knee joints and distal middle tibia presenting as patchy SPAIR high signals with unclear edge, in addition with edema of soft tissue surrounding the right distal femur. Majeed syndrome is characterized by chronic and recurrent multifocal osteomyelitis, congenital dyserythropoietic anemia, and growth retardation. Surrounding muscle tissue of osteomyelitis may also be involved. The syndrome may also affect the central nervous system, resulting in delayed language and motor development. Discovery of multiple pathological variants of the LPIN2 gene suggested that the clinical phenotype of this syndrome may vary between patients to some extent.

Next Generation Sequencing Based Multiplex Long-Range PCR for Routine Genotyping of Autoinflammatory Disorders

BackgroundDuring the last decade, remarkable progress with massive sequencing has been made in the identification of disease-associated genes for AIDs using next-generation sequencing technologies (NGS). An international group of experts described the ideal genetic screening method which should give information about SNVs, InDels, Copy Number Variations (CNVs), GC rich regions. We aimed to develop and validate a molecular diagnostic method in conjunction with the NGS platform as an inexpensive, extended and uniform coverage and fast screening tool which consists of nine genes known to be associated with various AIDs.MethodsFor the validation of basic and expanded panels, long-range multiplex models were setup on healthy samples without any known variations for MEFV, MVK, TNFRSF1A, NLRP3, PSTPIP1, IL1RN, NOD2, NLRP12 and LPIN2 genes. Patients with AIDs who had already known causative variants in these genes were sequenced for analytical validation. As a last step, multiplex models were validated on patients with pre-diagnosis of AIDs. All sequencing steps were performed on the Illumina NGS platform. Validity steps included the selection of related candidate genes, primer design, development of screening methods, validation and verification of the product. The GDPE (Gentera) bioinformatics pipeline was followed.ResultsAlthough there was no nonsynonymous variation in 21 healthy samples, 107 synonymous variant alleles and some intronic and UTR variants were detected. In 10 patients who underwent analytical validation, besides the 11 known nonsynonymous variant alleles, 11 additional nonsynonymous variant alleles and a total of 81 synonymous variants were found. In the clinical validation phase, 46 patients sequenced with multiplex panels, genetic and clinical findings were combined for diagnosis.ConclusionIn this study, we describe the development and validation of an NGS-based multiplex array enabling the “long-amplicon” approach for targeted sequencing of nine genes associated with common AIDs. This screening tool is less expensive and more comprehensive compared to other methods and more informative than traditional sequencing. The proposed panel offers advantages to WES or hybridization probe equivalents in terms of CNV analysis, high sensitivity and uniformity, GC-rich region sequencing, InDel detection and intron covering.

Identification of lipidomic profiles associated with drug-resistant prostate cancer cells

BackgroundThe association of circulating lipids with clinical outcomes of drug-resistant castration-resistant prostate cancer (DR-CRPC) is not fully understood. While it is known that increases in select lipids correlate to decreased survival, neither the mechanisms mediating these alterations nor the correlation of resistance to drug treatments is well characterized.MethodsThis gap-in-knowledge was addressed using in vitro models of non-cancerous, hormone-sensitive, CRPC and drug-resistant cell lines combined with quantitative LC-ESI-Orbitrap-MS (LC-ESI-MS/MS) lipidomic analysis and subsequent analysis such as Metaboanalyst and Lipid Pathway Enrichment Analysis (LIPEA).ResultsSeveral lipid regulatory pathways were identified that are associated with Docetaxel resistance in prostate cancer (PCa). These included those controlling glycerophospholipid metabolism, sphingolipid signaling and ferroptosis. In total, 7460 features were identified as being dysregulated between the cell lines studied, and 21 lipid species were significantly altered in drug-resistant cell lines as compared to nonresistant cell lines. Docetaxel resistance cells (PC3-Rx and DU145-DR) had higher levels of phosphatidylcholine (PC), oxidized lipid species, phosphatidylethanolamine (PE), and sphingomyelin (SM) as compared to parent control cells (PC-3 and DU-145). Alterations were also identified in the levels of phosphatidic acid (PA) and diacylglyceride (DAG), whose levels are regulated by Lipin (LPIN), a phosphatidic acid phosphatase that converts PA to DAG. Data derived from cBioPortal demonstrated a population of PCa patients expressing mutations aligning with amplification of LPIN1, LPIN2 and LPIN3 genes. Lipin amplification in these genes correlated to decreased survival in these patients. Lipin-1 mRNA expression also showed a similar trend in PCa patient data. Lipin-1, but not Lipin-2 or − 3, was detected in several prostate cancer cells, and was increased in 22RV1 and PC-3 cell lines. The increased expression of Lipin-1 in these cells correlated with the level of PA.ConclusionThese data identify lipids whose levels may correlate to Docetaxel sensitivity and progression of PCa. The data also suggest a correlation between the expression of Lipin-1 in cells and patients with regards to prostate cancer cell aggressiveness and patient survivability. Ultimately, these data may be useful for identifying markers of lethal and/or metastatic prostate cancer.

The Role of Genetic Mutations in Gene LPIN2 in Majeed Syndrome

Majeed syndrome is characterized by recurrent episodes of fever and inflammation in the bones and skin. The two main features of this condition are chronic recurrent multifocal osteomyelitis (CRMO) and congenital dyserythropoietic anemia (CDA). CRMO causes recurrent episodes of pain and joint swelling which can lead to complications such as slow growth and the development of joint deformities called contractures. CDA involves a shortage of red blood cells which can lead to fatigue (tiredness), weakness, pale skin, and shortness of breath. Most people with Majeed syndrome also develop inflammatory disorders of the skin, most often a condition known as Sweet syndrome. Majeed syndrome results from mutations in the LPIN2 gene. This condition is inherited in an autosomal recessive pattern

Next-generation screening of a panel of genes associated with periodic fever syndromes in patients with Familial Mediterranean Fever and their clinical characteristics

Familial Mediterranean Fever (FMF) is a hereditary fever syndrome that primarily affects Mediterranean populations. For the study, total number of 182 patients with FMF disease were enrolled and screening of a panel of genes , called “fever panel” which comprises 17 genes, was performed. The most common mutations in MEFV gene were homozygous M694V missense mutation (4.3%) and R202Q missense mutation (4.9%). The most common heterozygous mutations were R202Q (26.5%), M694V (25.9%) and E148Q (11.9%). Compound heterozygous and homozygous mutations were also detected. Also, different types of mutations were identified in NOD2, CARD14, NLRP12, NLRP3, NLRP7, IL1RN, LPIN2, TNFRSF1A, MVK and PSTPIP1 genes. Two novel missense variations in the MEFV gene, Gln34Pro and Ile247Val, which have not been previously reported in the databases, were identified. Also, Thr91Ile missense variation in the NOD2 gene, Gly461Cys missense variation in NLRP3 and Tyr732Stop nonsense variation in LPIN2 were firstly identified. The results of the current study suggest that in addition to the MEFV gene which has an important roles in FMF, molecular screening of other genes related to other autoinflammatory diseases might provide support in suspected cases and provide detailed information about the course of the disease.

Compound heterozygous LPIN2 pathogenic variants in a patient with Majeed syndrome with recurrent fever and severe neutropenia: case report

BackgroundMajeed syndrome is a rare, autosomal recessive autoinflammatory disorder first described in 1989. The syndrome starts during infancy with recurrent relapses of osteomyelitis typically associated with fever, congenital dyserythropoietic anemia (CDA), and often neutrophilic dermatosis. Mutations in the LPIN2 gene located on the short arm of chromosome 18 have been identified as being responsible for Majeed syndrome.Case presentationWe report an 8-month-old boy, who presented with recurrent fever, mild to moderate anemia, and severe neutropenia. Erythrocyte sedimentation rate and C-reactive protein were elevated. Molecular testing identified a paternal splicing donor site variant c.2327 + 1G > C and a maternal frameshift variant c.1691_1694delGAGA (Arg564Lysfs*3) in LPIN2.ConclusionsOnly a few cases with LPIN2 mutation have been reported, mainly in the Middle East with homozygous variants. Our patient exhibited a mild clinical phenotype and severe neutropenia, different from previous reports.

Ontogenetic Expression of Lpin2 and Lpin3 Genes and Their Associations with Traits in Two Breeds of Chinese Fat-tailed Sheep.

Lipins play dual function in lipid metabolism by serving as phosphatidate phosphatase and transcriptional co-regulators of gene expression. Mammalian lipin proteins consist of lipin1, lipin2, and lipin3 and are encoded by their respective genes Lpin1, Lpin2, and Lpin3. To date, most studies are concerned with Lpin1, only a few have addressed Lpin2 and Lpin3. Ontogenetic expression of Lpin2 and Lpin3 and their associations with traits would help to explore their molecular and physiological functions in sheep. In this study, 48 animals with an equal number of males and females each for both breeds of fat-tailed sheep such as Guangling Large Tailed (GLT) and Small Tailed Han (STH) were chosen to evaluate the ontogenetic expression of Lpin2 and Lpin3 from eight different tissues and months of age by quantitative real-time polymerase chain reaction (PCR). Associations between gene expression and slaughter and tail traits were also analyzed. The results showed that Lpin2 mRNA was highly expressed in perirenal and tail fats, and was also substantially expressed in liver, kidney, reproductive organs (testis and ovary), with the lowest levels in small intestine and femoral biceps. Lpin3 mRNA was prominently expressed in liver and small intestine, and was also expressed at high levels in kidney, perirenal and tail fats as well as reproductive organs (testis and ovary), with the lowest level in femoral biceps. Global expression of Lpin2 and Lpin3 in GLT both were significantly higher than those in STH. Spatiotemporal expression showed that the highest levels of Lpin2 expression occurred at 10 months of age in two breeds of sheep, with the lowest expression at 2 months of age in STH and at 8 months of age in GLT. The greatest levels of Lpin3 expression occurred at 4 months of age in STH and at 10 months of age in GLT, with the lowest expression at 12 months of age in STH and at 8 months of age in GLT. Breed and age significantly influenced the tissue expression patterns of Lpin2 and Lpin3, respectively, and sex significantly influenced the spatiotemporal expression patterns of Lpin3. Meanwhile, Lpin2 and Lpin3 mRNA expression both showed significant correlations with slaughter and tail traits, and the associations appear to be related with the ontogenetic expression as well as the potential functions of lipin2 and lipin3 in sheep.

Variation in the chicken LPIN2 gene and association with performance traits

The objective of the study was to investigate the distribution of LPIN2 variants and haplotypes among breeds and perform an association analysis of the variants and haplotypes with the broiler traits in chickens.Six breeds were used to study the variation and distribution of chicken LPIN2, and an F2 resource population was used to measure growth traits, carcass traits, meat quality traits and serum biochemistry parameters.A c.-599G>A variant was located in the promoter region of LPIN2 and c.444G>A and c.1730A>T (E577D) coding variant mutations were detected. Linkage disequilibrium tests showed that these three variants were under moderate linkage disequilibrium in the 6 breeds and 7 haplotypes were constructed. The distribution of variation/haplotypes presented clear differences among breeds.Association analysis showed that c.-599G>A was associated with leg muscle weight, jejunum length, ileum length, leg muscle fibre density and leg muscle fibre diameter; c.444G>A was associated with spleen weight, ileum length, body weight at hatch and metatarsus length at 8 weeks; c.1730T>A had significant effects on chicken liver weight, heart weight, body weight at 10 weeks, serum albumin and glucose.Diplotypes were significantly associated with body weight at hatch, heart weight, pancreas weight, duodenum length, leg muscle fibre density and lactate dehydrogenase.

Chromosomal structural variations during progression of a prostate epithelial cell line to a malignant metastatic state inactivate the NF2, NIPSNAP1, UGT2B17, and LPIN2 genes

Prostate cancer is the second highest cause of male cancer deaths in the United States. A significant number of tumors advance to a highly invasive and metastatic stage, which is typically resistant to traditional cancer therapeutics. In order to identify chromosomal structural variants that may contribute to prostate cancer progression we sequenced the genomes of a HPV-18 immortalized nonmalignant human prostate epithelial cell line, RWPE1, and compared it to its malignant, metastatic derivative, WPE1-NB26. There were a total of 34 large (>1 Mbp) and 38 small copy number variants (<100 kbp) in WPE1-NB26 that were not present in the precursor cell line. We also identified and validated 46 structural variants present in the two cell lines, of which 23 were unique to WPE1-NB26. Structural variants unique to the malignant cell line inactivated: (1) the neurofibromin2 (NF2) gene, a known tumor suppressor; (2) its neighboring gene NIPSNAP1, another putative tumor suppressor that inhibits TRPV6, an anti-apoptotic oncogene implicated in prostate cancer progression; (3) UGT2B17, a gene that inactivates dihydrotestosterone, a known activator of prostate cancer progression; and (4) LPIN2, a phosphatidic acid phosphatase and a co-factor of PGC1a that is important for lipid metabolism and for suppressing autoinflammation. Our results illustrate the value of comparing the genomes of defined related pairs of cell lines to discover chromosomal structural variants that may contribute to cancer progression.

SP0039 Immunological and genetic basis of CRMO

Chronicnon-bacterial osteomyelitis (CNO) is an inflammatory bone disorder of yet unknown origin. The clinical spectrum ranges from relatively benign, self-limiting, mono-focal symptoms to destructive, multi-focal involvement (known as chronic recurrent...

Study of LPIN1, LPIN2 and LPIN3 in rhabdomyolysis and exercise‐induced myalgia

Recessive LPIN1 mutations were identified as a cause of severe rhabdomyolysis in pediatric patients. The human lipin family includes two other closely related members, lipin-2 and 3, which share strong homology and similar activity. The study aimed to determine the involvement of the LPIN family genes in a cohort of pediatric and adult patients (n = 171) presenting with muscular symptoms, ranging from severe (CK >10 000 UI/L) or moderate (CK <10 000 UI/L) rhabdomyolysis (n = 141) to exercise-induced myalgia (n = 30), and to report the clinical findings in patients harboring mutations. Coding regions of LPIN1, LPIN2 and LPIN3 genes were sequenced using genomic or complementary DNAs. Eighteen patients harbored two LPIN1 mutations, including a frequent intragenic deletion. All presented with severe episodes of rhabdomyolysis, starting before age 6 years except two (8 and 42 years). Few patients also suffered from permanent muscle symptoms, including the eldest ones (≥ 40 years). Around 3/4 of muscle biopsies showed accumulation of lipid droplets. At least 40% of heterozygous relatives presented muscular myalgia. Nine heterozygous SNPs in LPIN family genes were identified in milder phenotypes (mild rhabdomyolysis or myalgia). These variants were non-functional in yeast complementation assay based on respiratory activity, except the LPIN3-P24L variant. LPIN1-related myolysis constitutes a major cause of early-onset rhabdomyolysis and occasionally in adults. Heterozygous LPIN1 mutations may cause mild muscular symptoms. No major defects of LPIN2 or LPIN3 genes were associated with muscular manifestations.

Characterization of the LPIN2 Gene and its Protein and Examination of its Role in Psoriasis

Psoriasis is a chronic inflammatory skin disease posing a considerable worldwide health problem due to its high prevalence, associated morbidity and high health-care costs. It is a multifactorial “complex” disorder, with compelling evidence for a genetic predisposition. On the other hand, Majeed syndrome, a Mendelian disorder of bone and skin inflammation is caused by homozygous mutations in LPIN2. Many observations have implicated LPIN2 in the genetic etiology of psoriasis, including its position in a psoriasis locus. We identified several non-synonymous SNPs within the LPIN2 in patients with psoriasis that are not present in healthy controls. We hypothesize that the variations in LPIN2 play a role in the susceptibility to development of psoriasis and that LPIN2 is the psoriasis susceptibility locus on 18p. We aim to examine this hypothesis by examining the properties of the wild type and mutant proteins, as well as examining any difference in function between the wild type and mutants. We have obtained custom synthesized cDNA clones encoding the full Lipin2 wild type protein and the six identified mutant proteins (p.K387E, p.S734L, p.A331S, p.L504F, p.P348L, p.E601K). The cDNA clones were subcloned into pYES2 vector for expression in yeast cells (Saccharomyces cerevisiae). Each construct was transformed into Saccharomyces cerevisiae for protein expression. The analysis utilizes SDS Gel Electophoresis and Western Blot. The DNA analysis indicates that each fragment has been correctly cloned into the pYES2 vector. The analyses using SDS Gel Electrophoresis and Western Blot indicate that the Wild type and p.K387E are successfully expressed in S. cerevisiae while p.S734L is expressed in S. cerevisiae but at a lower level. Expression experiments are being done on the 4 remaining mutant proteins. We were successful in artificially expressing the human Lipin2 protein in its different forms in yeast cells. We are currently optimizing the conditions to produce substantial amounts of the proteins to be studied by Circular dichroism to determine the folding patterns. Other methods will be approached to study the function.

Novel mutation of the LPIN2 gene in Turkish brothers with Majeed syndrome. Response to IL-1 inhibition

Background Majeed syndrome is a rare, syndromic form of chronic recurrent multifocal osteomyelitis (CRMO) first described in 1989. The syndrome starts during infancy with recurrent relapses of osteomyelitis typically associated with fever, congenital dyserythropoietic anemia (CDA) and often neutrophilic dermatosis (Sweet syndrome). Homozygous mutations in the LPIN2 gene located on the short arm of chromosome 18 have been identified as being responsible for the Majeed syndrome. Aim To report a novel mutation in the LPIN2 gene detected in two brothers with Majeed syndrome and to describe the clinical characteristics and response to treatment. Case presentations Two Turkish brothers (13 (Y) and 29 (M) months old) with consanguinity of the parents were admitted with relapsing episodes of pain and ‘pseudoparalysis’ of upper and lower extremities since the age of 3 and 6 months, respectively. No concomitant fever has occurred during the attacks. Whole body MRI of the elder brother (M) revealed osteomyelitic changes of the metaphyses of tibiae, left fibula and left radius. Biopsy from lesions showed no malignancy and negative bacterial cultures. Both showed significant hypersedimentation (ESR 92 mm/hr (Y) and 96 mm/hr (M)), slight thrombocytosis, and moderate anemia (Hb 9.0 (Y) and 9.7 (M) g/dl). Bone marrow aspiration was consistent with congenital dyserythropoietic anemia (CDA) with 6% - 9% bi- or multinucleated erythrocytes. LPIN2 gene re-sequencing of each affected child revealed a homozygous 2 bp deletion (c.1312_1313delCT) resulting in an early truncation of the protein (L438fs+16X), which confirmed the diagnosis in both patients. Clinically, both were refractory to the treatment with corticosteroids and TNFa inhibition (etanercept). Elevated plasma levels of proinflammatory cytokines (IL-1b ,I L-6, IL-8, TNFa) did not change significantly during the treatment. In M, rapid clinical and laboratory improvement was observed after introduction with anakinra (1.7 mg/kg/d), which has not yet been introduced to Y. Conclusion We describe a novel mutation of the LPIN2 gene in two Turkish brothers with Majeed syndrome. Although our patients also presented with CDA none of them had fever during the attacks nor dermatological changes unlike previously described patients with Majeed. IL-1 inhibition showed promising clinical and laboratory results.

Characterization of the LPIN2 gene and its protein and examination of its role in psoriasis

Psoriasis is a chronic inflammatory skin disease posing a considerable world-wide health problem due to its high prevalence, associated morbidity and high health-care costs. It is a multifactorial “complex” disorder, with compelling evidence for a genetic predisposition. Majeed syndrome is a Mendelian disorder with a consistent phenotype and its causative gene can be examined for its role in the more common bone and skin inflammatory disorders of complex etiology. Majeed syndrome is caused by mutations in LPIN2. Many observations have implicated LPIN2 in the genetic etiology of psoriasis. Based on these observations, we hypothesize that variations in LPIN2 play a role in the susceptibility to development of psoriasis and that LPIN2 is the psoriasis susceptibility locus on 18p. In our previous study, we identified 6 coding variants that may be associated with psoriasis due to the fact that they change evolutionary conserved amino acids and they are present in the general population at a very low allele frequency. However, the ultimate evidence of their causation of the phenotype is to prove that there is a change in protein properties or function with the molecular variations. One of the aims of the current work is to shed light on whether each identified LPIN2 mutation has an effect on the integrity of the properties of the Lipin2 protein and therefore its function. The wide type and six different cDNA LPIN2 clones, each harboring one of the six described variations were successfully synthesised after codon optimisation for maximum expression in yeast. The LPIN2 gene and two mutants were excised from its original construct and inserted into similarly digested pYES2. The newly formed constructs were transformed into competent cells of Saccharomyces cerevisiae for protein expression. Our preliminary analyses using SDS gel electrophoresis and Western blot indicate that the wild type and the two mutants are expressed in S. cerevisiae but at a low level. Optimization of the expression as well as expression of these genes in different expression system is being carried out. The recombinant protein of the wild type LPIN2 and the two mutants will be subjected to circular dichroism and fluorescence measurements to study the effect of each mutant on the folding and therefore the function of the protein.

The lipin family: mutations and metabolism

The family of three lipin proteins act as phosphatidate phosphatase (PAP) enzymes required for glycerolipid biosynthesis, and also as transcriptional coactivators that regulate expression of lipid metabolism genes. The genes for lipin-1, lipin-2 and lipin-3 are expressed in key metabolic tissues, including adipose tissue, skeletal muscle and liver, but the physiological functions of each member of the family have not been fully elucidated. Here we examine the most recent studies that provide information about the roles of lipin proteins in metabolism and human disease. Recent studies have identified mutations that cause lipin-1 or lipin-2 deficiency in humans, leading to acute myoglobinuria in childhood or the inflammatory disorder Majeed syndrome, respectively. The effects of lipin-1 deficiency appear to include both the loss of glycerolipid building blocks and the accumulation of lipid intermediates that disrupt cellular function. Several studies have demonstrated that polymorphisms in the LPIN1 and LPIN2 genes are associated with metabolic disease traits, including insulin sensitivity, diabetes, blood pressure and response to thiazolidinedione drugs. Furthermore, lipin-1 expression levels in adipose tissue and/or liver are positively correlated with insulin sensitivity. Studies of lipin-1 in adipocytes have shed some light on its relationship with insulin sensitivity. Lipin-1 and lipin-2 are required for normal lipid homeostasis and have unique physiological roles. Future studies, for example using engineered mouse models, will be required to fully elucidate their specific roles in normal physiology and disease.

LPIN2 Is Associated With Type 2 Diabetes, Glucose Metabolism, and Body Composition

To identify the type 2 diabetes gene located at chromosome 18p11. We investigated the region in a young genetically isolated population by genotyping 34 single nucleotide polymorphisms (SNPs) in 78 case subjects and 101 control subjects. Two SNPs were selected and followed up in two cohorts. The first cohort came from a general Dutch population. In this cohort, association with type 2 diabetes was investigated using 616 type 2 diabetic case subjects and 2,890 control subjects; association with oral glucose tolerance test data was performed in 361 normoglycemic people. Association with fat distribution was studied in the second replication cohort, consisting of 836 people from the genetically isolated population. At the initial step, we found that the common C allele of SNP rs3745012 was associated with type 2 diabetes (odds ratio 2.01, P = 0.03). This SNP is located at the 3' untranslated region of the LPIN2 gene, which is a plausible candidate for type 2 diabetes and obesity. In the cohort from the general Dutch population, we demonstrated that rs3745012 interacts with BMI in determination of type 2 diabetes: whereas in subjects with high BMI, the common C allele is associated with type 2 diabetes, the same allele exhibits a neutral or protective effect in lean subjects (P = 0.05 overall effect, P = 0.02 interaction). Most remarkably, rs3745012 strongly affected composite insulin sensitivity index (P = 0.006 for overall effect, P = 0.004 for interaction). In the second replication cohort, we found that the allele C of rs3745012 increases trunk-to-legs fat mass ratio (P = 0.001) and may affect other fat-related measurements. rs3745012 SNP of the LPIN2 gene is associated with type 2 diabetes and fat distribution.

Evaluation of Lipin 2 as a candidate gene for autosomal dominant 1 high-grade myopia

The first autosomal dominant high-grade myopia locus has been mapped to chromosome 18p11.31 between markers D18S59 and D18S1138 by haplotype analysis. Refinement of the region by transmission disequilibrium testing suggests that a candidate gene (or genes) for this locus named myopia 2 ( MYP2) is likely in an interval between markers D18S63 and D18S52. Lipin 2 ( LPIN2), a candidate gene for lipodystrophy, maps in proximity to this locus. Our purpose in this study was to identify mutations and polymorphisms in the LPIN2 gene in myopic patients and control subjects. Expression studies of this gene by reverse transcription-polymerase chain reaction (RT-PCR) showed that LPIN2 was ubiquitously expressed in various tissues, such as brain, kidney, lung, heart, and skeletal muscles. It was also expressed in cornea, lens, retina, optic nerve, and sclera. Direct sequencing of the LPIN2 gene revealed 11 single nucleotide polymorphisms (SNPs) in myopia and unaffected individuals. Eight of them were novel. Among the 11 SNPs detected in this study, 2 exonic variants (G2950692A and C2924436T) were synonymous and do not lead to changes in amino acid of the translated protein product. Two transversions in intron 1 (T2951033A homozygote and heterozygote, C2951049A) and one transversions in intron 7 (G2924536C homozygote and heterozygote), 5 nucleotide variants (A 2909606T, del2909343T, G2907798C, T2907425G, T2907152C) in the 3′-untranslated region (3′-UTR), and TATTAA nucleotide deletions (homozygote and heterozygote) at 2950970-5 in intron 1 were also detected. Although LPIN2 gene was excluded as a candidate for MYP2, the SNPs detected in this study will aid in future mapping and association studies involving this gene.