A prognostic marker LTBP1 is associated with epithelial mesenchymal transition and can promote the progression of gastric cancer

LTBP1 is closely related to TGF-β1 function as an essential component, which was unclear in gastric cancer (GC). Harbin Medical University (HMU)-GC cohort and The Cancer Genome Atlas (TCGA) dataset were combined to form a training cohort to calculate the connection between LTBP1 mRNA expression, prognosis and clinicopathological features. The training cohort was also used to verify the biological function of LTBP1 and its relationship with immune microenvironment and chemosensitivity. In the tissue microarrays (TMAs), immunohistochemical (IHC) staining was performed to observe LTBP1 protein expression. The correlation between LTBP1 protein expression level and prognosis was also analyzed, and a nomogram model was constructed. Western blotting (WB) was used in cell lines to assess LTBP1 expression. Transwell assays and CCK-8 were employed to assess LTBP1's biological roles. In compared to normal gastric tissues, LTBP1 expression was upregulated in GC tissues, and high expression was linked to a bad prognosis for GC patients. Based on a gene enrichment analysis, LTBP1 was primarily enriched in the TGF-β and EMT signaling pathways. Furthermore, high expression of LTBP1 in the tumor microenvironment was positively correlated with an immunosuppressive response. We also found that LTBP1 expression (p = 0.006) and metastatic lymph node ratio (p = 0.044) were independent prognostic risk factors for GC patients. The prognostic model combining LTBP1 expression and lymph node metastasis ratio reliably predicted the prognosis of GC patients. In vitro proliferation and invasion of MKN-45 GC cells were inhibited and their viability was decreased by LTBP1 knockout. LTBP1 plays an essential role in the development and progression of GC, and is a potential prognostic biomarker and therapeutic target for GC.

Weill-Marchesani syndrome: natural history and genotype-phenotype correlations from 18 news cases and review of literature

BACKGROUND

Weill-Marchesani syndrome (WMS) belongs to the group of acromelic dysplasias, defined by short stature, brachydactyly and joint limitations. WMS is characterised by specific ophthalmological abnormalities, although cardiovascular defects have also been reported. Monoallelic variations in FBN1 are associated with a dominant form of WMS, while biallelic variations in ADAMTS10, ADAMTS17 and LTBP2 are responsible for a recessive form of WMS.

OBJECTIVE

Natural history description of WMS and genotype-phenotype correlation establishment.

MATERIALS AND METHODS

Retrospective multicentre study and literature review.

INCLUSION CRITERIA

clinical diagnosis of WMS with identified pathogenic variants.

RESULTS

61 patients were included: 18 individuals from our cohort and 43 patients from literature. 21 had variants in ADAMTS17, 19 in FBN1, 19 in ADAMTS10 and 2 in LTBP2. All individuals presented with eye anomalies, mainly spherophakia (42/61) and ectopia lentis (39/61). Short stature was present in 73% (from -2.2 to -5.5 SD), 10/61 individuals had valvulopathy. Regarding FBN1 variants, patients with a variant located in transforming growth factor (TGF)-β-binding protein-like domain 5 (TB5) domain were significantly smaller than patients with FBN1 variant outside TB5 domain (p=0.0040).

CONCLUSION

Apart from the ophthalmological findings, which are mandatory for the diagnosis, the phenotype of WMS seems to be more variable than initially described, partially explained by genotype-phenotype correlation.

The IAAM LTBP4 Haplotype is Protective Against Dystrophin-Deficient Cardiomyopathy

Background

Dilated cardiomyopathy (DCM) is a major complication of, and leading cause of mortality in Duchenne muscular dystrophy (DMD). Its severity, age at onset, and rate of progression display wide variability, whose molecular bases have been scarcely elucidated. Potential DCM-modifying factors include glucocorticoid (GC) and cardiological treatments, DMD mutation type and location, and variants in other genes.

Methods and Results

We retrospectively collected 3138 echocardiographic measurements of left ventricular ejection fraction (EF), shortening fraction (SF), and end-diastolic volume (EDV) from 819 DMD participants, 541 from an Italian multicentric cohort and 278 from the Cooperative International Neuromuscular Group Duchenne Natural History Study (CINRG-DNHS). Using generalized estimating equation (GEE) models, we estimated the yearly rate of decrease of EF (-0.80%) and SF (-0.41%), while EDV increase was not significantly associated with age. Utilizing a multivariate generalized estimating equation (GEE) model we observed that mutations preserving the expression of the C-terminal Dp71 isoform of dystrophin were correlated with decreased EDV (-11.01 mL/m2, p = 0.03) while for dp116 were correlated with decreased EF (-4.14%, p = <0.001). The rs10880 genotype in the LTBP4 gene, previously shown to prolong ambulation, was also associated with increased EF and decreased EDV (+3.29%, p = 0.002, and -10.62 mL/m2, p = 0.008) with a recessive model.

Conclusions

We quantitatively describe the progression of systolic dysfunction progression in DMD, confirm the effect of distal dystrophin isoform expression on the dystrophin-deficient heart, and identify a strong effect of LTBP4 genotype of DCM in DMD.

Analysis of glaucoma genes in Finnish patients with juvenile open-angle glaucoma

PURPOSE

To identify germline variants in myocilin (MYOC) and other known monogenic glaucoma genes in Finnish patients with juvenile open-angle glaucoma (JOAG).

METHODS

Finnish patients with JOAG treated between 2010 and 2018 at the Department of Ophthalmology, Helsinki University Hospital, Finland, were enrolled. We sequenced all exonic regions and flanking splice sites of MYOC for five patients and one healthy relative using Sanger sequencing. In 48 patients, we performed exome sequencing to identify variants also in 28 other glaucoma-related genes.

RESULTS

Fifty-three individuals with JOAG from 50 pedigrees, and one healthy relative, participated. The mean age at diagnosis was 30.8 years [SD 7.6; range 11 to 39]. Five probands had probably pathogenic variants in MYOC: c.1102C>T p.(Gln368Ter), c.1109C>T p.(Pro370Leu), c.1130C>T p.(Thr377Met), c.1132G>A p.(Asp378Asn) and c.1456C>T p.(Leu486Phe). Four of these patients had a family history of dominantly inherited JOAG. The frequency of MYOC variants was 10% (5 of 50 families). One patient and his mother with JOAG had a novel loss-of-function variant in the FOXC1 gene, c.366G>A p.(Trp122Ter). A patient with sporadic JOAG had a homozygous likely pathogenic variant in the LTBP2 gene, c.3938G>A p.(Cys1313Tyr). The genetic variants explained 14% (7 out of 50 families; 95% CI, 6%-23%) of JOAG in our cohort.

CONCLUSIONS

The frequency of pathogenic variants in previously known glaucoma-associated genes is low in Finnish patients with JOAG. Because of the distinct genetic background of Finns, it might be possible to identify novel glaucoma genes through our JOAG series in the future.

Identification and phenotypic analysis of novel LTBP2 mutations in a Chinese cohort with congenital ectopia lentis

Purpose

To evaluate the frequency of LTBP2 mutations and to elaborate on LTBP2-related clinical phenotypes in a Chinese congenital ectopia lentis (CEL) cohort.

Methods

In total, 145 Chinese probands with CEL were recruited for this study and underwent ocular and systemic examinations. Whole-exome sequencing was used to identify mutations, and Sanger sequencing and bioinformatics analysis were further performed to verify pathogenic mutations.

Results

Overall, biallelic mutations in LTBP2 involving eight novel mutations (c.4370-7_4370-9delTCT, c.4370-5C>G, c.3452G>A, c.2253delG, c.4114T>C, c.1251G>A, c.4760G>A, and c.620G>A) were identified in four CEL probands (4/145, 2.76%). Patients with LTBP2 mutations were characterized by a megalocornea, spherophakia, high myopia, and glaucoma instead of a flat cornea, high corneal astigmatism, cardiovascular and skeletal abnormalities that were reported in other gene mutations. A novel homozygous frameshift mutation was detected, and this type of mutation was found to cause more complicated ocular symptoms than others, ranging from the anterior segment to the fundus.

Conclusion

This study reported the mutation frequency of the LTBP2 gene in a Chinese CEL cohort and provided novel insight into LTBP2-related genotype-phenotype associations in CEL.

circWHSC1: A circular RNA piece in the human cancer puzzle

Circular RNAs (circRNAs) are a group of non-coding RNAs with a closed loop shape, which are transcribed via non-canonical splicing. They are mainly formed by reverse splicing of a precursor mRNA. circWHSC1 (Hsa_circ_0001387), is a cancer-related circRNA that originated from the Wolf-Hirschhorn syndrome candidate 1 (WHSC1) gene on chromosome 4. circWHSC1 has been found to be overexpressed in different neoplastic conditions. circWHSC1 acts as a sponge for many different miRNAs, including miR-195-5p, miR-532-3p, miR-646, miR-142-3p, miR-7, miR-296-3p, miR-145, miR-1182, miR-212-5p, etc. It can also moderate several signaling pathways, including FASN/AMPK/mTOR, LTBP2, NPM1, HOXA1, TAB2, AKT3, hTERT, and MUC1. Studies have shown that circWHSC1 may leads to an increase in cell growth, tumor size, cell migration, invasion, and metastasis, but a reduction in apoptosis rates. Moreover, upregulation of CircWHSC1 has been associated with reduced patient's survival in different cancers, representing the function of this circRNA as a novel prognostic marker. Nevertheless, there are no reviews focusing on the relationship between circWHSC1 and cancers. Therefore, in the current review, we will first describe the oncogenic effect of circWHSC1 in various tissues according to the evidence from in vitro, in vivo, and human studies.

Characteristics and genotype-phenotype correlations in ADAMTS17 mutation-related Weill-Marchesani syndrome

Weill-Marchesani syndrome (WMS) manifests as ectopia lentis (EL), microspherophakia and short stature, which is caused by ADAMTS10, LTBP2, or ADAMTS17 gene defects. This study aims to investigate the characteristics and genotype-phenotype correlations of WMS with ADAMTS17 mutations. WMS patients with ADAMTS17 variants were identified by whole-exome sequencing from 185 patients with EL. All the included patients underwent comprehensive ocular and systemic examinations. ADAMTS17 variants were reviewed from included patients, published literature, and public databases. Bioinformatics analysis, co-segregation analysis, species sequence analysis, and protein silico modeling were used to verify the pathogenic mutations. A total of six novel ADAMTS17 mutations (c.1297C > T, c.2948C > T, c.1322+2T > C, c.1716C > G, c.1630G > A, and c.1669C > T) were identified in four WMS probands in our EL cohort (4/185, 2.16%). All probands and their biological parents presented with apparent short stature compared with the standard value. In particular, one child was detected with valvular heart disease, which has not previously been reported in patients with ADAMTS17 mutations. Conserved residues were greatly affected by the substitution of amino acids caused by these six mutations. Short stature could be considered a clue for EL patients with ADAMTS17 mutations, and much more attention needs to be paid to heart disorders among these patients. This study not only reported the characteristics of ADAMTS17 mutation-related WMS but also helped to recognize the genotype-phenotype correlations in these patients.

Compound Heterozygous LTBP2 Mutations Associated With Juvenile-Onset Open-Angle Glaucoma and Marfan-Like Phenotype

This case report describes a patient diagnosed at age 13 years with glaucoma who later presented with elevated intraocular pressure, severe cupping, open iridocorneal angle, and lens dislocation.

The Role of Genetic Testing in Children Requiring Surgery for Ectopia Lentis

Non-traumatic ectopia lentis can be isolated or herald an underlying multisystemic disorder. Technological advances have revolutionized genetic testing for many ophthalmic disorders, and this study aims to provide insights into the clinical utility of genetic analysis in paediatric ectopia lentis. Children that underwent lens extraction for ectopia lentis between 2013 and 2017 were identified, and gene panel testing findings and surgical outcomes were collected. Overall, 10/11 cases received a probable molecular diagnosis. Genetic variants were identified in four genes: FBN1 (associated with Marfan syndrome and cardiovascular complications; n = 6), ADAMTSL4 (associated with non-syndromic ectopia lentis; n = 2), LTBP2 (n = 1) and ASPH (n = 1). Parents appeared unaffected in 6/11 cases; the initial presentation of all six of these children was to an ophthalmologist, and only 2/6 had FBN1 variants. Notably, 4/11 cases required surgery before the age of 4 years, and only one of these children carried an FBN1 variant. In summary, in this retrospective cohort study, panel-based genetic testing pointed to a molecular diagnosis in >90% of paediatric ectopia lentis cases requiring surgery. In a subset of study participants, genetic analysis revealed changes in genes that have not been linked to extraocular manifestations and highlighted that extensive systemic investigations were not required in these individuals. We propose the introduction of genetic testing early in the diagnostic pathway in children with ectopia lentis.

Exome-based mutation screening in South African children with primary congenital glaucoma

OBJECTIVES

To identify pathogenic variants in a cohort of 23 black South African children with sporadic primary congenital glaucoma (PCG) using an exome-based approach.

METHODS

Children with PCG were recruited from two Paediatric Ophthalmology Clinics in Johannesburg, South Africa. Whole exome sequencing was performed on genomic DNA. Of the 23 children, 19 were male and 19 had bilateral PCG. A variant prioritization strategy was employed whereby variants in known PCG genes (CYP1B1, LTBP2 and TEK) were evaluated first, followed by the identification of putative disease-causing variants in other genes related to eye diseases and phenotypes.

RESULTS

Validated pathogenic variants in the CYP1B1 gene (c.1169 G>A; p.Arg390His) and TEK gene (c.922 G>A; p.Gly308Arg) were identified in one child each. No LTBP2 mutations were identified in this cohort. In silico predictions identified potentially damaging rare variants in genes previously associated with eye development phenotypes or glaucoma in a further 12 children.

CONCLUSIONS

This study demonstrates the value of whole exome sequencing in identifying disease-causing variants in African children with PCG. It is the first report of a TEK disease-causing variant in an African PCG patient. Potential causative variants detected in PCG candidate genes warrant further investigation.

ADAMTS6 cleaves the large latent TGFβ complex and increases the mechanotension of cells to activate TGFβ

The ADAMTS superfamily is composed of secreted metalloproteases and structurally related non-catalytic ADAMTS-like proteins. A subset of this superfamily, including ADAMTS6, ADAMTS10 and ADAMTSL2, are involved in elastic fiber assembly and bind to fibrillin and other matrix molecules that regulate the extracellular bioavailability of the potent growth factor TGFβ. Fibrillinopathies, that can also result from mutation of these ADAMTS/L proteins, have been linked to disrupted TGFβ homeostasis. ADAMTS6 and ADAMTS10 are homologous metalloproteases with poorly characterized substrates where ADAMTS10 is thought to process fibrillin-2 and ADAMTS6 latent TGFβ-binding protein (LTBP)-1. In order to understand the contribution of ADAMTS6, and these other members of the ADAMTS/L family, to TGFβ homeostasis, we have analyzed the effects of ADAMTS6, ADAMTS10 and ADAMTSL2 expression on TGFβ activation. We found that their expression increases TGFβ activation in a dose dependent manner, following stimulation with mature TGFβ1. For ADAMTS6, the catalytically active protease is required for effective TGFβ activation, where ADAMTS6 cleaves LTBP3 as well as LTBP1, and binds to the large latent TGFβ complexes of LTBP1 and LTBP3. Furthermore, ADAMTS6 expression increases the mechanotension of cells which results in inactivation of the Hippo Pathway, resulting in an increased translocation of YAP/TAZ complex to the nucleus. Together these findings suggest that when the balance of TGFβ is perturbed ADAMTS6 can influence TGFβ activation via two mechanisms. It directly cleaves the latent TGFβ complexes and also acts indirectly, along with ADAMTS10 and ADAMTSL2, by altering the mechanotension of cells. Together this increases activation of TGFβ from large latent complexes which may contribute to disease pathogenesis.

LTBP4, SPP1, and CD40 Variants: Genetic Modifiers of Duchenne Muscular Dystrophy Analyzed in Serbian Patients

Background: Clinical course variability in Duchenne muscular dystrophy (DMD) is partially explained by the mutation location in the DMD gene and variants in modifier genes. We assessed the effect of the SPP1, CD40, and LTBP4 genes and DMD mutation location on loss of ambulation (LoA). Methods: SNPs in SPP1-rs28357094, LTBP4-rs2303729, rs1131620, rs1051303, rs10880, and CD40-rs1883832 were genotyped, and their effect was assessed by survival and hierarchical cluster analysis. Results: Patients on glucocorticoid corticosteroid (GC) therapy experienced LoA one year later (p = 0.04). The modifying effect of SPP1 and CD40 variants, as well as LTBP4 haplotypes, was not observed using a log-rank test and multivariant Cox regression analysis. Cluster analysis revealed two subgroups with statistical trends in differences in age at LoA. Almost all patients in the cluster with later LoA had the protective IAAM LTBP4 haplotype and statistically significantly fewer CD40 genotypes with harmful T allele and “distal” DMD mutations. Conclusions: The modifying effect of SPP1, CD40, and LTBP4 was not replicated in Serbian patients, although our cohort was comparable in terms of its DMD mutation type distribution, SNP allele frequencies, and GC-positive effect with other European cohorts. Cluster analysis may be able to identify patient subgroups carrying a combination of the genetic variants that modify LoA.

Elevated latent transforming growth factor beta binding protein 2 in endometriosis promotes endometrial stromal cell invasion and proliferation via the NF-kB signaling pathway

Endometriosis, defined as the abnormal growth of functional endometrium outside the uterus, is characterized by the abnormal phenotype of endometrial cells. This study aimed to investigate the role of latent transforming growth factor beta binding protein 2 (LTBP2), an extracellular matrix protein, in the occurrence and development of endometriosis. Elevated LTBP2 expression levels were observed in endometrial tissues and serum of endometriosis patients and their area under the ROC curve (AUC) values for distinguishing endometriosis were 0.9044 and 0.9534, respectively. Overexpressing-LTBP2 could promote proliferation, migration, and invasion, whereas suppressing apoptosis of endometrial stromal cells (ESCs). Moreover, LTBP2 downregulation induced the opposite effect. The supernatant from ESCs overexpressing LTBP2 promoted the tube formation of human umbilical vein endothelial cells (HUVECs), thus indicating an angiogenic effect. Furthermore, overexpression of LTBP2 facilitated the inflammation and might promote endometriosis progression through the NF-kB signaling pathway. Conclusively, LTBP2 might be a potential target in the diagnosis and treatment of endometriosis.

Aberrant interaction between mutated ADAMTSL2 and LTBP4 is associated with adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a complex spinal structure deformity with a prevalence of 1%-3%. Genetic and hereditary factors have been associated with the etiology of AIS. However, previous studies mainly focused on common single nucleotide polymorphisms which confer modest disease risk. Recently, rare variants in FBN1 and other extracellular matrix genes have been implicated in AIS, suggesting a potential overlapping disease etiology between AIS and hereditary connective tissue disorders (HCTD). In this study, we systematically analyzed rare variants in a set of HCTD-related genes in 302 AIS patients using exome sequencing. We firstly focused on pathogenic variants based on a monogenic inheritance and identified nine disease-associated variants in FBN1, COL11A1, COL11A2 and TGFBR2. We then explored the potential interactions between variants in different genes based on the case-control statistics. We identified three ADAMTSL2-LTBP4 variant pairs in three AIS patients and none in controls. Furthermore, we revealed that the variant pairs identified in these genes could affect the interaction between ADAMTSL2 and LTBP4 and upregulate TGF-β signaling pathway in human fibroblasts. Our findings supported that the aberrant interaction between mutated ADAMTSL2 and LTBP4 was associated with AIS.

Identification of triple gene fusion ALK-LRRN2, LTBP1-ALK, and HIP1-ALK in advanced lung adenocarcinoma and response to alectinib: A case report

RATIONALE

Anaplastic lymphoma kinase (ALK) rearrangement is the second most common targetable oncogene-dirven gene in nonsmall cell lung cancer. Owing to the advanced sequencing technologies, new partner genes of ALK have been constantly detected.

PATIENT CONCERNS

A 42-year-old Chinese woman went to our hospital with the chief complaint of cough and expectoration for 1 month. The patient had no fever, chest pain, and hemoptysis.

DIAGNOSES

She was diagnosed with advanced lung adenocarcinoma. The patient underwent lung biopsy guided by computed tomography and pathology showed poorly differentiated adenocarcinoma. To explore possibility of targeted therapy, the tumor samples were subjected to next-generation sequencing, and a rare 3 ALK fusion variant ALK-LRRN2, LTBP1-ALK, and HIP1-ALK was identified.

INTERVENTIONS AND OUTCOMES

The patient subsequently received alectinib treatment, and achieved partial response. No significant drug related adverse reactions were found during alectinib treatment. The progression-free survival achieved 25 months.

LESSONS

Together, we identified a rare triple ALK fusion variant, ALK-LRRN2, LTBP1-ALK and HIP1-ALK, in a patient with lung adenocarcinoma. The patient benefited from alectinib treatment, which could provide a certain reference for the patients with such gene alteration.

POGLUT2 and POGLUT3 O-glucosylate multiple EGF repeats in fibrillin-1, -2, and LTBP1 and promote secretion of fibrillin-1

Fibrillin-1 (FBN1) is the major component of extracellular matrix microfibrils, which are required for proper development of elastic tissues, including the heart and lungs. Through protein-protein interactions with latent transforming growth factor (TGF) β-binding protein 1 (LTBP1), microfibrils regulate TGF-β signaling. Mutations within the 47 epidermal growth factor-like (EGF) repeats of FBN1 cause autosomal dominant disorders including Marfan Syndrome, which is characterized by disrupted TGF-β signaling. We recently identified two novel protein O-glucosyltransferases, Protein O-glucosyltransferase 2 (POGLUT2) and 3 (POGLUT3), that modify a small fraction of EGF repeats on Notch. Here, using mass spectral analysis, we show that POGLUT2 and POGLUT3 also modify over half of the EGF repeats on FBN1, fibrillin-2 (FBN2), and LTBP1. While most sites are modified by both enzymes, some sites show a preference for either POGLUT2 or POGLUT3. POGLUT2 and POGLUT3 are homologs of POGLUT1, which stabilizes Notch proteins by addition of O-glucose to Notch EGF repeats. Like POGLUT1, POGLUT2 and 3 can discern a folded versus unfolded EGF repeat, suggesting POGLUT2 and 3 are involved in a protein folding pathway. In vitro secretion assays using the N-terminal portion of recombinant FBN1 revealed reduced FBN1 secretion in POGLUT2 knockout, POGLUT3 knockout, and POGLUT2 and 3 double-knockout HEK293T cells compared with wild type. These results illustrate that POGLUT2 and 3 function together to O-glucosylate protein substrates and that these modifications play a role in the secretion of substrate proteins. It will be interesting to see how disease variants in these proteins affect their O-glucosylation.

Latent TGF-β1 protects against diabetic kidney disease via Arkadia/Smad7 signaling

TGF-β1 has long been considered as a key mediator in diabetic kidney disease (DKD) but anti-TGF-β1 treatment fails clinically, suggesting a diverse role for TGF-β1 in DKD. In the present study, we examined a novel hypothesis that latent TGF-β1 may be protective in DKD mice overexpressing human latent TGF-β1. Streptozotocin-induced Type 1 diabetes was induced in latent TGF-β1 transgenic (Tg) and wild-type (WT) mice. Surprisingly, compared to WT diabetic mice, mice overexpressing latent TGF-β1 were protected from the development of DKD as demonstrated by lowing microalbuminuria and inhibiting renal fibrosis and inflammation, although blood glucose levels were not altered. Mechanistically, the renal protective effects of latent TGF-β1 on DKD were associated with inactivation of both TGF-β/Smad and nuclear factor-κB (NF-κB) signaling pathways. These protective effects were associated with the prevention of renal Smad7 from the Arkadia-induced ubiquitin proteasomal degradation in the diabetic kidney, suggesting protection of renal Smad7 from Arkadia-mediated degradation may be a key mechanism through which latent TGF-β1 inhibits DKD. This was further confirmed in vitro in mesangial cells that knockdown of Arkadia failed but overexpression of Arkadia reversed the protective effects of latent TGF-β1 on high glucose-treated mesangial cells. Latent TGF-β1 may protect kidneys from TGF-β1/Smad3-mediated renal fibrosis and NF-κB-driven renal inflammation in diabetes through inhibiting Arkadia-mediated Smad7 ubiquitin degradation.

Bi-allelic premature truncating variants in LTBP1 cause cutis laxa syndrome

Latent transforming growth factor β (TGFβ)-binding proteins (LTBPs) are microfibril-associated proteins essential for anchoring TGFβ in the extracellular matrix (ECM) as well as for correct assembly of ECM components. Variants in LTBP2, LTBP3, and LTBP4 have been identified in several autosomal recessive Mendelian disorders with skeletal abnormalities with or without impaired development of elastin-rich tissues. Thus far, the human phenotype associated with LTBP1 deficiency has remained enigmatic. In this study, we report homozygous premature truncating LTBP1 variants in eight affected individuals from four unrelated consanguineous families. Affected individuals present with connective tissue features (cutis laxa and inguinal hernia), craniofacial dysmorphology, variable heart defects, and prominent skeletal features (craniosynostosis, short stature, brachydactyly, and syndactyly). In vitro studies on proband-derived dermal fibroblasts indicate distinct molecular mechanisms depending on the position of the variant in LTBP1. C-terminal variants lead to an altered LTBP1 loosely anchored in the microfibrillar network and cause increased ECM deposition in cultured fibroblasts associated with excessive TGFβ growth factor activation and signaling. In contrast, N-terminal truncation results in a loss of LTBP1 that does not alter TGFβ levels or ECM assembly. In vivo validation with two independent zebrafish lines carrying mutations in ltbp1 induce abnormal collagen fibrillogenesis in skin and intervertebral ligaments and ectopic bone formation on the vertebrae. In addition, one of the mutant zebrafish lines shows voluminous and hypo-mineralized vertebrae. Overall, our findings in humans and zebrafish show that LTBP1 function is crucial for skin and bone ECM assembly and homeostasis.

LTBP4 in Health and Disease

Latent transforming growth factor β (TGFβ)-binding protein (LTBP) 4, a member of the LTBP family, shows structural homology with fibrillins. Both these protein types are characterized by calcium-binding epidermal growth factor-like repeats interspersed with 8-cysteine domains. Based on its domain composition and distribution, LTBP4 is thought to adopt an extended structure, facilitating the linear deposition of tropoelastin onto microfibrils. In humans, mutations in LTBP4 result in autosomal recessive cutis laxa type 1C, characterized by redundant skin, pulmonary emphysema, and valvular heart disease. LTBP4 is an essential regulator of TGFβ signaling and is related to development, immunity, injury repair, and diseases, playing a central role in regulating inflammation, fibrosis, and cancer progression. In this review, we focus on medical disorders or diseases that may be manipulated by LTBP4 in order to enhance the understanding of this protein.

Bi-allelic LoF NRROS Variants Impairing Active TGF-β1 Delivery Cause a Severe Infantile-Onset Neurodegenerative Condition with Intracranial Calcification

Negative regulator of reactive oxygen species (NRROS) is a leucine-rich repeat-containing protein that uniquely associates with latent transforming growth factor beta-1 (TGF- β1) and anchors it on the cell surface; this anchoring is required for activation of TGF-β1 in macrophages and microglia. We report six individuals from four families with bi-allelic variants in NRROS. All affected individuals had neurodegenerative disease with refractory epilepsy, developmental regression, and reduced white matter volume with delayed myelination. The clinical course in affected individuals began with normal development or mild developmental delay, and the onset of seizures occurred within the first year of life, followed by developmental regression. Intracranial calcification was detected in three individuals. The phenotypic features in affected individuals are consistent with those observed in the Nrros knockout mouse, and they overlap with those seen in the human condition associated with TGF-β1 deficiency. The disease-causing NRROS variants involve two significant functional NRROS domains. These variants result in aberrant NRROS proteins with impaired ability to anchor latent TGF-β1 on the cell surface. Using confocal microscopy in HEK293T cells, we demonstrate that wild-type and mutant NRROS proteins co-localize with latent TGF-β1 intracellularly. However, using flow cytometry, we show that our mutant NRROS proteins fail to anchor latent TGF-β1 at the cell surface in comparison to wild-type NRROS. Moreover, wild-type NRROS rescues the defect of our disease-associated mutants in presenting latent TGF-β1 to the cell surface. Taken together, our findings suggest that loss of NRROS function causes a severe childhood-onset neurodegenerative condition with features suggestive of a disordered response to inflammation.

Novel mutations in LTBP2 identified in familial cases of primary congenital glaucoma

Purpose

Primary congenital glaucoma (PCG) is a genetically heterogeneous disorder caused by developmental defects in the anterior chamber and trabecular meshwork. This disease is an important cause of childhood blindness. In this study, we aim to identify the genetic determinants of PCG in three consanguineous families of Pakistani descent.

Methods

Affected members of all three families underwent detailed ophthalmological examination including slit-lamp biomicroscopy. Blood samples were collected from affected and healthy members of all three families, and genomic DNA was extracted. Linkage analysis was performed for the known or reported loci of PCG to localize the disease interval, and logarithm of odds (LOD) scores were calculated. All protein-coding exons of the candidate gene, latent transforming growth factor-beta binding protein 2 (LTBP2), were bidirectionally sequenced to identify the disease-causing mutation.

Results

Short tandem repeat (STR) marker-based linkage analysis localized the critical interval to chromosome 14q with a maximum two-point LOD score of 2.86 (PKGL076), 2.8 (PKGL015), and 2.92 (PKGL042). Bidirectional Sanger sequencing of LTBP2 revealed three novel pathogenic variants, i.e., c.3028G>A (p.Asp1010Asn), c.3427delC (p.Gln1143Argfs*35), and c.5270G>A (p.Cys1757Tyr) in PKGL076, PKGL015, and PKGL042, respectively. All three mutations segregated with the disease phenotype in their respective families and were absent in 200 ethnically matched normal chromosomes.

Conclusions

We identified three novel mutations, p.D1010N, p.Q1143Rfs*35, and p.C1757Y, in LTBP2 responsible for PCG.

LRRC33 is a novel binding and potential regulating protein of TGF-β1 function in human acute myeloid leukemia cells

Transforming growth factor‑β1 (TGF-β1) is a versatile cytokine. It has context-dependent pro- and anti-cell proliferation functions. Activation of latent TGF-β1 requires release of the growth factor from pro-complexes and is regulated through TGF-β binding proteins. Two types of TGF-β binding partners, latent TGF-β-binding proteins (LTBPs) and leucine-rich-repeat-containing protein 32 (LRRC32), have been identified and their expression are cell specific. TGF-β1 also plays important roles in acute myeloid leukemia (AML) cells. However, the expression of LTBPs and LRRC32 are lacking in myeloid lineage cells and the binding protein of TGF-β1 in these cells are unknown. Here we show that a novel leucine-rich-repeat-containing protein family member, LRRC33, with high mRNA level in AML cells, to be the binding and regulating protein of TGF-β1 in AML cells. Using two representative cell lines MV4-11 and AML193, we demonstrate that the protein expression of LRRC33 and TGF-β1 are correlated. LRRC33 co-localizes and forms complex with latent TGF-β1 protein on the cell surface and intracellularly in these cells. Similar as in other cell types, the activation of TGF-β1 in MV4-11 and AML193 cells are also integrin dependent. We anticipate our study to be a starting point of more comprehensive research on LRRC33 as novel TGF-β regulating protein and potential non-genomic based drug target for AML and other myeloid malignancy.

Proteomic discovery of substrates of the cardiovascular protease ADAMTS7

The protease ADAMTS7 functions in the extracellular matrix (ECM) of the cardiovascular system. However, its physiological substrate specificity and mechanism of regulation remain to be explored. To address this, we conducted an unbiased substrate analysis using terminal amine isotopic labeling of substrates (TAILS). The analysis identified candidate substrates of ADAMTS7 in the human fibroblast secretome, including proteins with a wide range of functions, such as collagenous and noncollagenous extracellular matrix proteins, growth factors, proteases, and cell-surface receptors. It also suggested that autolysis occurs at Glu-729-Val-730 and Glu-732-Ala-733 in the ADAMTS7 Spacer domain, which was corroborated by N-terminal sequencing and Western blotting. Importantly, TAILS also identified proteolysis of the latent TGF-β-binding proteins 3 and 4 (LTBP3/4) at a Glu-Val and Glu-Ala site, respectively. Using purified enzyme and substrate, we confirmed ADAMTS7-catalyzed proteolysis of recombinant LTBP4. Moreover, we identified multiple additional scissile bonds in an N-terminal linker region of LTBP4 that connects fibulin-5/tropoelastin and fibrillin-1-binding regions, which have an important role in elastogenesis. ADAMTS7-mediated cleavage of LTBP4 was efficiently inhibited by the metalloprotease inhibitor TIMP-4, but not by TIMP-1 and less efficiently by TIMP-2 and TIMP-3. As TIMP-4 expression is prevalent in cardiovascular tissues, we propose that TIMP-4 represents the primary endogenous ADAMTS7 inhibitor. In summary, our findings reveal LTBP4 as an ADAMTS7 substrate, whose cleavage may potentially impact elastogenesis in the cardiovascular system. We also identify TIMP-4 as a likely physiological ADAMTS7 inhibitor.

Genotype-phenotype correlation and expansion of orodental anomalies in LTBP3-related disorders

The latent transforming growth factor-beta-binding protein 3 (LTBP3), encoding extracellular matrix proteins, plays a role in skeletal formation. Mutations in LTBP3 have been associated with various types of skeletal dysplasia. We aimed to characterize clinical and molecular features of more patients with mutations in the gene, which may help suggest genotype-phenotype correlation. The first two East Asian patients with short stature, heart defects, and orodental anomalies having LTBP3 mutations were identified. Whole exome and Sanger sequencing revealed that the one with a novel heterozygous missense (c.2017G>T, p.Gly673Cys) mutation in LTBP3 had clinical features consistent with acromicric dysplasia (ACMICD). The variant was located in the highly conserved EGF-like calcium-binding domain adjacent to the single reported LTBP3 variant associated with ACMICD. This finding supports that LTBP3 is a disease gene for ACMICD. Another patient with a novel homozygous splice site acceptor (c.1721-2A>G) mutation in LTBP3 was affected with dental anomalies and short stature (DASS). Previously undescribed orodental features included multiple unerupted teeth, high-arched palate, and microstomia found in our patient with ACMICD, and extensive dental infection, condensing osteitis, and deviated alveolar bone formation in our patient with DASS. Our results and comprehensive reviews suggest a genotype-phenotype correlation: biallelic loss-of-function mutations cause DASS, monoallelic missense gain-of-function mutations in the EGF-like domain cause ACMICD, and monoallelic missense gain-of-function mutations with more drastic effects on the protein functions cause geleophysic dysplasia (GPHYSD3). In summary, we expand the phenotypic and genotypic spectra of LTBP3-related disorders, support that LTBP3 is a disease gene for ACMICD, and propose the genotype-phenotype correlation of LTBP3 mutations.

The fibronectin ED-A domain enhances recruitment of latent TGF-β-binding protein-1 to the fibroblast matrix

Dysregulated secretion and extracellular activation of TGF-β1 stimulates myofibroblasts to accumulate disordered and stiff extracellular matrix (ECM) leading to fibrosis. Fibronectin immobilizes latent TGF-β-binding protein-1 (LTBP-1) and thus stores TGF-β1 in the ECM. Because the ED-A fibronectin splice variant is prominently expressed during fibrosis and supports myofibroblast activation, we investigated whether ED-A promotes LTBP-1-fibronectin interactions. Using stiffness-tuneable substrates for human dermal fibroblast cultures, we showed that high ECM stiffness promotes expression and colocalization of LTBP-1 and ED-A-containing fibronectin. When rescuing fibronectin-depleted fibroblasts with specific fibronectin splice variants, LTBP-1 bound more efficiently to ED-A-containing fibronectin than to ED-B-containing fibronectin and fibronectin lacking splice domains. Function blocking of the ED-A domain using antibodies and competitive peptides resulted in reduced LTBP-1 binding to ED-A-containing fibronectin, reduced LTBP-1 incorporation into the fibroblast ECM and reduced TGF-β1 activation. Similar results were obtained by blocking the heparin-binding stretch FNIII12-13-14 (HepII), adjacent to the ED-A domain in fibronectin. Collectively, our results suggest that the ED-A domain enhances association of the latent TGF-β1 by promoting weak direct binding to LTBP-1 and by enhancing heparin-mediated protein interactions through HepII in fibronectin.

Rapid Communication: High-resolution quantitative trait loci analysis identifies LTBP2 encoding latent transforming growth factor beta binding protein 2 associated with thoracic vertebrae number in a large F2 intercross between Landrace and Korean native pigs

Number of vertebrae is associated with body size and meat productivity in pigs. The aim of this study was to identify QTL and associated positional candidate genes affecting the number of thoracic vertebrae (THO). A genomewide association study was conducted in a large resource population derived from an F intercross between Landrace and Korean native pigs using the Porcine SNP 60K BeadChip and the genomewide complex trait analysis (GCTA) program based on a linear mixed-effects model. A total of 38,385 SNP markers from 1,105 F progeny were analyzed for the THO trait after filtering for quality control. A total of 90 genomewide significant SNP markers ( < 1.30 × 10) on SSC 7 covering a 20-Mb region were identified for THO in this study. Several previous studies also mapped QTL for vertebral numbers in this region. The strongest association signals were detected at ASGA0035500 (-value = 4.46 × 10; 103,574,383 bp) and DIAS0000795 (-value = 4.46 × 10; 103,594,753 bp). The QTL region on SSC 7 for THO encompasses and , which are previously described candidate genes for vertebral number variation. To refine the QTL region, a haplotype-based linkage and linkage disequilibrium (LALD) analysis using the DualPHASE program was applied because subsequent conditional association and haplotype block analyses could not resolve the region that contains the 2 loci. The LALD analysis refined the critical region to a 533.9-kb region including ; was located outside the critical region. The gene encoding latent transforming growth factor beta binding protein 2 is involved in bone metabolisms. Based on these data, we propose as a positional candidate gene for THO in pigs. After further functional studies and verification of the association in other independent populations, these results could be useful for optimizing breeding programs that improve THO and other economically important traits in pigs.

Primary congenital and developmental glaucomas

Glaucoma is the leading cause of irreversible blindness worldwide. Although most glaucoma patients are elderly, congenital glaucoma and glaucomas of childhood are also important causes of visual disability. Primary congenital glaucoma (PCG) is isolated, non-syndromic glaucoma that occurs in the first three years of life and is a major cause of childhood blindness. Other early-onset glaucomas may arise secondary to developmental abnormalities, such as glaucomas that occur with aniridia or as part of Axenfeld-Rieger syndrome. Congenital and childhood glaucomas have strong genetic bases and disease-causing mutations have been discovered in several genes. Mutations in three genes (CYP1B1, LTBP2, TEK) have been reported in PCG patients. Axenfeld-Rieger syndrome is caused by mutations in PITX2 or FOXC1 and aniridia is caused by PAX6 mutations. This review discusses the roles of these genes in primary congenital glaucoma and glaucomas of childhood.

Sex differences in the development of prolactinoma in mice overexpressing hCGβ: role of TGFβ1

Female transgenic mice that overexpress the human chorionic gonadotrophin β subunit (hCGβ+) develop prolactinomas, whereas hCGβ+ males do not. The high levels of circulating hCG induce massive luteinization in the ovary of hCGβ+ females, and progesterone becomes the primary steroid hormone produced, but estradiol remains at physiological level. The involvement of high levels of progesterone in lactotroph proliferation is not clearly understood; hence, the pathogenesis of prolactinomas in hCGβ+ females remains unclear. TGFβ1 is an inhibitor of lactotroph function, and the reduced TGFβ1 activity found in prolactinomas has been proposed to be involved in tumor development. The aim of the present work was to study the role of TGFβ1 in the gender-specific development of prolactinomas in hCGβ+ mice. We compared the expression of different components of the pituitary TGFβ1 system in males and females in this model. We found reduced TGFβ1 levels, reduced expression of TGFβ1 target genes, TGFβ1 receptors, Ltbp1, Smad4 and Smad7 in hCGβ+ female pituitaries. However, no differences were found between the transgenic and wild-type male pituitaries. We postulate that decreased pituitary TGFβ1 activity in hCGβ+ females is involved in the development of prolactinomas. In fact, we demonstrated that an in vivo treatment carried out for increasing pituitary TGFβ1 activity, was successful in reducing the prolactinoma development, and the hyperprolactinemia in hCGβ+ females. Moreover, the stronger TGFβ1 system found in males could protect them from excessive lactotroph proliferation. Sex differences in the regulation of the pituitary TGFβ1 system could explain gender differences in the incidence of prolactinoma.

Latent TGF-β binding protein-1 deficiency decreases female fertility

The four latent transforming growth factor-β (TGF-β) binding proteins LTBP1-4 are extracellular matrix-associated proteins playing a critical role in the activation of TGF-β. The LTBP1 gene forms two major transcript variants (i.e. Ltbp1S and Ltbp1L) that are derived from different promoters. We have previously shown the importance of LTBP1 in vivo by using three different Ltbp1 null mice that were either deleted for exons 1 and 2 (Ltbp1L knockout), exon 5 (Ltbp1ΔEx5), or exon 8 (Ltbp1ΔEx8). While the Ltbp1L knockout and the Ltbp1ΔEx8 are perinatal lethal and die of cardiovascular abnormalities, the Ltbp1ΔEx5 is viable because it expresses a short form of Ltbp1L that lacks 55 amino acids (Δ55 variant of Ltbp1) formed by splicing out exon 5, while lacking the Ltbp1S variant. Since only the Ltbp1ΔEx5 mouse is viable, we have used this model to address aspects of puberty, fertility, age-dependent reproduction, and ovary function. We report for the first time a function of LTBP1 in female reproduction. The Ltbp1ΔEx5 females showed impaired fertility associated with delayed sexual maturity (p = 0.0074) and ovarian cyst formation in females older than 40 weeks (p = 0.0204).

Association Study of Exon Variants in the NF-κB and TGFβ Pathways Identifies CD40 as a Modifier of Duchenne Muscular Dystrophy

The expressivity of Mendelian diseases can be influenced by factors independent from the pathogenic mutation: in Duchenne muscular dystrophy (DMD), for instance, age at loss of ambulation (LoA) varies between individuals whose DMD mutations all abolish dystrophin expression. This suggests the existence of trans-acting variants in modifier genes. Common single nucleotide polymorphisms (SNPs) in candidate genes (SPP1, encoding osteopontin, and LTBP4, encoding latent transforming growth factor β [TGFβ]-binding protein 4) have been established as DMD modifiers. We performed a genome-wide association study of age at LoA in a sub-cohort of European or European American ancestry (n = 109) from the Cooperative International Research Group Duchenne Natural History Study (CINRG-DNHS). We focused on protein-altering variants (Exome Chip) and included glucocorticoid treatment as a covariate. As expected, due to the small population size, no SNPs displayed an exome-wide significant p value (< 1.8 × 10^-6). Subsequently, we prioritized 438 SNPs in the vicinities of 384 genes implicated in DMD-related pathways, i.e., the nuclear-factor-κB and TGFβ pathways. The minor allele at rs1883832, in the 5'-untranslated region of CD40, was associated with earlier LoA (p = 3.5 × 10^-5). This allele diminishes the expression of CD40, a co-stimulatory molecule for T cell polarization. We validated this association in multiple independent DMD cohorts (United Dystrophinopathy Project, Bio-NMD, and Padova, total n = 660), establishing this locus as a DMD modifier. This finding points to cell-mediated immunity as a relevant pathogenetic mechanism and potential therapeutic target in DMD.

A Mutation in LTBP2 Causes Congenital Glaucoma in Domestic Cats (Felis catus)

The glaucomas are a group of diseases characterized by optic nerve damage that together represent a leading cause of blindness in the human population and in domestic animals. Here we report a mutation in LTBP2 that causes primary congenital glaucoma (PCG) in domestic cats. We identified a spontaneous form of PCG in cats and established a breeding colony segregating for PCG consistent with fully penetrant, autosomal recessive inheritance of the trait. Elevated intraocular pressure, globe enlargement and elongated ciliary processes were consistently observed in all affected cats by 8 weeks of age. Varying degrees of optic nerve damage resulted by 6 months of age. Although subtle lens zonular instability was a common feature in this cohort, pronounced ectopia lentis was identified in less than 10% of cats examined. Thus, glaucoma in this pedigree is attributed to histologically confirmed arrest in the early post-natal development of the aqueous humor outflow pathways in the anterior segment of the eyes of affected animals. Using a candidate gene approach, significant linkage was established on cat chromosome B3 (LOD 18.38, θ = 0.00) using tightly linked short tandem repeat (STR) loci to the candidate gene, LTBP2. A 4 base-pair insertion was identified in exon 8 of LTBP2 in affected individuals that generates a frame shift that completely alters the downstream open reading frame and eliminates functional domains. Thus, we describe the first spontaneous and highly penetrant non-rodent model of PCG identifying a valuable animal model for primary glaucoma that closely resembles the human disease, providing valuable insights into mechanisms underlying the disease and a valuable animal model for testing therapies.

Mutations in LTBP3 cause acromicric dysplasia and geleophysic dysplasia

BACKGROUND

Acromelic dysplasias are a group of disorders characterised by short stature, brachydactyly, limited joint extension and thickened skin and comprises acromicric dysplasia (AD), geleophysic dysplasia (GD), Myhre syndrome and Weill-Marchesani syndrome. Mutations in several genes have been identified for these disorders (including latent transforming growth factor β (TGF-β)-binding protein-2 (LTBP2), ADAMTS10, ADAMSTS17 and fibrillin-1 (FBN1) for Weill-Marchesani syndrome, ADAMTSL2 for recessive GD and FBN1 for AD and dominant GD), encoding proteins involved in the microfibrillar network. However, not all cases have mutations in these genes.

METHODS

Individuals negative for mutations in known acromelic dysplasia genes underwent whole exome sequencing.

RESULTS

A heterozygous missense mutation (exon 14: c.2087C>G: p.Ser696Cys) in latent transforming growth factor β (TGF-β)-binding protein-3 (LTBP3) was identified in a dominant AD family. Two distinct de novo heterozygous LTPB3 mutations were also identified in two unrelated GD individuals who had died in early childhood from respiratory failure-a donor splice site mutation (exon 12 c.1846+5G>A) and a stop-loss mutation (exon 28: c.3912A>T: p.1304*Cysext*12).

CONCLUSIONS

The constellation of features in these AD and GD cases, including postnatal growth retardation of long bones and lung involvement, is reminiscent of the null ltbp3 mice phenotype. We conclude that LTBP3 is a novel component of the microfibrillar network involved in the acromelic dysplasia spectrum.

Genotype-Specific Interaction of Latent TGFβ Binding Protein 4 with TGFβ

Latent TGFβ binding proteins are extracellular matrix proteins that bind latent TGFβ to form the large latent complex. Nonsynonymous polymorphisms in LTBP4, a member of the latent TGFβ binding protein gene family, have been linked to several human diseases, underscoring the importance of TGFβ regulation for a range of phenotypes. Because of strong linkage disequilibrium across the LTBP4 gene, humans have two main LTBP4 alleles that differ at four amino acid positions, referred to as IAAM and VTTT for the encoded residues. VTTT is considered the “risk” allele and associates with increased intracellular TGFβ signaling and more deleterious phenotypes in muscular dystrophy and other diseases. We now evaluated LTBP4 nsSNPs in dilated cardiomyopathy, a distinct disorder associated with TGFβ signaling. We stratified based on self-identified ethnicity and found that the LTBP4 VTTT allele is associated with increased risk of dilated cardiomyopathy in European Americans extending the diseases that associate with LTBP4 genotype. However, the association of LTBP4 SNPs with dilated cardiomyopathy was not observed in African Americans. To elucidate the mechanism by which LTBP4 genotype exerts this differential effect, TGFβ’s association with LTBP4 protein was examined. LTBP4 protein with the IAAM residues bound more latent TGFβ compared to the LTBP4 VTTT protein. Together these data provide support that LTBP4 genotype exerts its effect through differential avidity for TGFβ accounting for the differences in TGFβ signaling attributed to these two alleles.

Genetic Modifiers of Duchenne Muscular Dystrophy and Dilated Cardiomyopathy

OBJECTIVE

Dilated cardiomyopathy (DCM) is a major complication and leading cause of death in Duchenne muscular dystrophy (DMD). DCM onset is variable, suggesting modifier effects of genetic or environmental factors. We aimed to determine if polymorphisms previously associated with age at loss of independent ambulation (LoA) in DMD (rs28357094 in the SPP1 promoter, rs10880 and the VTTT/IAAM haplotype in LTBP4) also modify DCM onset.

METHODS

A multicentric cohort of 178 DMD patients was genotyped by TaqMan assays. We performed a time-to-event analysis of DCM onset, with age as time variable, and finding of left ventricular ejection fraction < 50% and/or end diastolic volume > 70 mL/m2 as event (confirmed by a previous normal exam < 12 months prior); DCM-free patients were censored at the age of last echocardiographic follow-up.

RESULTS

Patients were followed up to an average age of 15.9 ± 6.7 years. Seventy-one/178 patients developed DCM, and median age at onset was 20.0 years. Glucocorticoid corticosteroid treatment (n = 88 untreated; n = 75 treated; n = 15 unknown) did not have a significant independent effect on DCM onset. Cardiological medications were not administered before DCM onset in this population. We observed trends towards a protective effect of the dominant G allele at SPP1 rs28357094 and recessive T allele at LTBP4 rs10880, which was statistically significant in steroid-treated patients for LTBP4 rs10880 (< 50% T/T patients developing DCM during follow-up [n = 13]; median DCM onset 17.6 years for C/C-C/T, log-rank p = 0.027).

CONCLUSIONS

We report a putative protective effect of DMD genetic modifiers on the development of cardiac complications, that might aid in risk stratification if confirmed in independent cohorts.

Cerebral small vessel disease-related protease HtrA1 processes latent TGF-β binding protein 1 and facilitates TGF-β signaling

High temperature requirement protein A1 (HtrA1) is a primarily secreted serine protease involved in a variety of cellular processes including transforming growth factor β (TGF-β) signaling. Loss of its activity causes cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), an inherited form of cerebral small vessel disease leading to early-onset stroke and premature dementia. Dysregulated TGF-β signaling is considered to promote CARASIL pathogenesis, but the underlying molecular mechanisms are incompletely understood. Here we present evidence from mouse brain tissue and embryonic fibroblasts as well as patient skin fibroblasts for a facilitating role of HtrA1 in TGF-β pathway activation. We identify latent TGF-β binding protein 1 (LTBP-1), an extracellular matrix protein and key regulator of TGF-β bioavailability, as a novel HtrA1 target. Cleavage occurs at physiological protease concentrations, is prevented under HtrA1-deficient conditions as well as by CARASIL mutations and disrupts both LTBP-1 binding to fibronectin and its incorporation into the extracellular matrix. Hence, our data suggest an attenuation of TGF-β signaling caused by a lack of HtrA1-mediated LTBP-1 processing as mechanism underlying CARASIL pathogenesis.

Transcriptional profiling of the human fibrillin/LTBP gene family, key regulators of mesenchymal cell functions

The fibrillins and latent transforming growth factor binding proteins (LTBPs) form a superfamily of extracellular matrix (ECM) proteins characterized by the presence of a unique domain, the 8-cysteine transforming growth factor beta (TGFβ) binding domain. These proteins are involved in the structure of the extracellular matrix and controlling the bioavailability of TGFβ family members. Genes encoding these proteins show differential expression in mesenchymal cell types which synthesize the extracellular matrix. We have investigated the promoter regions of the seven gene family members using the FANTOM5 CAGE database for human. While the protein and nucleotide sequences show considerable sequence similarity, the promoter regions were quite diverse. Most genes had a single predominant transcription start site region but LTBP1 and LTBP4 had two regions initiating different transcripts. Most of the family members were expressed in a range of mesenchymal and other cell types, often associated with use of alternative promoters or transcription start sites within a promoter in different cell types. FBN3 was the lowest expressed gene, and was found only in embryonic and fetal tissues. The different promoters for one gene were more similar to each other in expression than to promoters of the other family members. Notably expression of all 22 LTBP2 promoters was tightly correlated and quite distinct from all other family members. We located candidate enhancer regions likely to be involved in expression of the genes. Each gene was associated with a unique subset of transcription factors across multiple promoters although several motifs including MAZ, SP1, GTF2I and KLF4 showed overrepresentation across the gene family. FBN1 and FBN2, which had similar expression patterns, were regulated by different transcription factors. This study highlights the role of alternative transcription start sites in regulating the tissue specificity of closely related genes and suggests that this important class of extracellular matrix proteins is subject to subtle regulatory variations that explain the differential roles of members of this gene family.

Latent transforming growth factor β-binding protein 4 is downregulated in esophageal cancer via promoter methylation

Latent transforming growth factor β-binding protein 4 (LTBP4) is an extracellular matrix molecule that is a member of important connective tissue networks and is needed for the correct folding and the secretion of TGF-β1. LTBP4 is downregulated in carcinomas of various tissues. Here we show that LTBP4 is also downregulated in adenocarcinomas and squamous cell carcinomas of the esophagus in vitro and in vivo. Re-expression of LTBP4 in esophageal cancer cell lines reduced cell migration ability, whereas cell viability and cell proliferation remained unchanged. Hypermethylation of the promoter regions of the two main human LTBP4 transcriptional forms, LTBP4L and LTBP4S, was found to be involved in LTBP4 silencing. Detailed investigations of the methylation patterns of the promoter regions of LTBP4L and LTBP4S identified GATA1, SP1, E2F4 and SMAD3 as potential transcription factors involved in LTBP4 expression. In in vitro transcription factor activity studies we discovered E2F4 as novel powerful regulator for LTBP4S expression.

Structure and function of the mammalian fibrillin gene family: implications for human connective tissue diseases

Fibrillins and latent transforming growth factor β binding proteins (LTBPs) are components of the extracellular matrix of connective tissue. While fibrillins are integral to the 10nm microfibrils, and often associated with elastin, all family members are likely to have an additional role in regulating the bioavailability of transforming growth factor β (TGBβ). Both fibrillins and LTBPs are large glycoproteins, containing a series of calcium binding epidermal growth factor domains as well as a number of copies of a unique 8 cysteine domain found only in this protein superfamily. There are three mammalian fibrillins and four LTBPs. Fibrillin monomers link head to tail in microfibrils which can then form two and three dimensional structures. In some tissues elastin is recruited to the fibrillin microfibrils to provide elasticity to the tissue. LTBPs are part of the TGBβ large latent complex which sequesters TGBβ in the extracellular matrix. Fibrillin-1 appears to bind to LTBPs to assist in this process and is thus involved in regulating the bioavailability of TGBβ. Mutation of fibrillin genes results in connective tissue phenotypes which reflect both the increased level of active TGBβ and the structural failure of the extracellular matrix due to the absence or abnormality of fibrillin protein. Fibrillinopathies include Marfan syndrome, familial ectopia lentis, familial thoracic aneurysm (mutations of FBN1) and congenital contractural arachnodactyly (mutation of FBN2). There are no diseases currently associated with mutation of FBN3 in humans, and this gene is no longer active in rodents. Expression patterns of fibrillin genes are consistent with their role in extracellular matrix structure of connective tissue. FBN1 expression is high in most cell types of mesenchymal origin, particularly bone. Human and mouse FBN2 expression is high in fetal cells and has more restricted expression in mesenchymal cell types postnatally. FBN3 is expressed early in development (embryonic and fetal tissues) in humans. The fibrillins are thus important in maintaining the structure and integrity of the extracellular matrix and, in combination with their sequence family members the LTBPs, also contribute to the regulation of the TGFβ family of major growth factors.

Regulation of TGF-β storage and activation in the human idiopathic pulmonary fibrosis lung

Idiopathic pulmonary fibrosis (IPF) is a progressive disease of unknown cause. The pathogenesis of the disease is characterized by fibroblast accumulation and excessive transforming growth factor-β (TGF-β) activation. Although TGF-β activation is a complex process involving various protein interactions, little is known of the specific routes of TGF-β storage and activation in human lung. Here, we have systematically analyzed the expression of specific proteins involved in extracellular matrix targeting and activation of TGF-β. Latent TGF-β-binding protein (LTBP)-1 was found to be significantly upregulated in IPF patient lungs. LTBP-1 expression was especially high in the fibroblastic foci, in which P-Smad2 immunoreactivity, indicative of TGF-β signaling activity, was less prominent. In cultured primary lung fibroblasts and epithelial cells, short-interfering-RNA-mediated downregulation of LTBP-1 resulted in either increased or decreased TGF-β signaling activity, respectively, suggesting that LTBP-1-mediated TGF-β activation is dependent on the cellular context in the lung. Furthermore, LTBP-1 was shown to colocalize with fibronectin, fibrillin-1 and fibrillin-2 proteins in the IPF lung. Fibrillin-2, a developmental gene expressed only in blood vessels in normal adult lung, was found specifically upregulated in IPF fibroblastic foci. The TGF-β-activating integrin β8 subunit was expressed at low levels in both control and IPF lungs. Alterations in extracellular matrix composition, such as high levels of the TGF-β storage protein LTBP-1 and the re-appearance of fibrillin-2, probably modulate TGF-β availability and activation in different pulmonary compartments in the fibrotic lung.

Microenvironmental regulation by fibrillin-1

Fibrillin-1 is a ubiquitous extracellular matrix molecule that sequesters latent growth factor complexes. A role for fibrillin-1 in specifying tissue microenvironments has not been elucidated, even though the concept that fibrillin-1 provides extracellular control of growth factor signaling is currently appreciated. Mutations in FBN1 are mainly responsible for the Marfan syndrome (MFS), recognized by its pleiotropic clinical features including tall stature and arachnodactyly, aortic dilatation and dissection, and ectopia lentis. Each of the many different mutations in FBN1 known to cause MFS must lead to similar clinical features through common mechanisms, proceeding principally through the activation of TGFβ signaling. Here we show that a novel FBN1 mutation in a family with Weill-Marchesani syndrome (WMS) causes thick skin, short stature, and brachydactyly when replicated in mice. WMS mice confirm that this mutation does not cause MFS. The mutation deletes three domains in fibrillin-1, abolishing a binding site utilized by ADAMTSLIKE-2, -3, -6, and papilin. Our results place these ADAMTSLIKE proteins in a molecular pathway involving fibrillin-1 and ADAMTS-10. Investigations of microfibril ultrastructure in WMS humans and mice demonstrate that modulation of the fibrillin microfibril scaffold can influence local tissue microenvironments and link fibrillin-1 function to skin homeostasis and the regulation of dermal collagen production. Hence, pathogenetic mechanisms caused by dysregulated WMS microenvironments diverge from Marfan pathogenetic mechanisms, which lead to broad activation of TGFβ signaling in multiple tissues. We conclude that local tissue-specific microenvironments, affected in WMS, are maintained by a fibrillin-1 microfibril scaffold, modulated by ADAMTSLIKE proteins in concert with ADAMTS enzymes.

The microenvironment is specified by cell-surface molecules, growth factors, and the extracellular matrix. Here we report genetic evidence that implicates fibrillin-1, a ubiquitous extracellular matrix molecule that sequesters latent growth factor complexes, as a key determinant in the local control of musculoskeletal and skin microenvironments. A novel mutation in fibrillin-1 demonstrates that modulation of the fibrillin microfibril scaffold can influence tissue microenvironments and result in the clinical features of Weill-Marchesani syndrome (WMS), including thick skin, short stature, and brachydactyly. Dysregulated WMS microenvironments diverge from Marfan pathogenetic mechanisms, which lead to broad activation of TGFβ signaling in multiple tissues.

Molecular characterization of newborn glaucoma including a distinct aniridic phenotype

PURPOSE

To characterize the underlying genetic defect in otherwise healthy Saudi newborns with buphthalmos, including those with iris abnormalities.

METHODS

Prospective case series of affected Saudi Arabian probands who were referred for genetic counseling over a 4 year period. All had CYP1B1 sequencing. Selected patients with visible iris abnormalities had PAX6, FOXC1, and PITX2 sequencing. CYP1B1-negative patients had LTBP2 sequencing.

RESULTS

All 67 probands had corneal enlargement with variable haze/scarring evident to caregivers at birth; 46 had a family history of infantile or early childhood glaucoma. All families were consanguineous except for 6, 2 of which were endogamous. Eight probands had mild ectropion uveae with partial aniridia; 2 probands had thick scarred corneas that precluded careful iris examination. Homozygous or compound heterozygous CYP1B1 mutations were identified in 91% (61/67), including all 8 probands with ectopion uveae and partial aniridia. The common Saudi mutation p.G61E occurred in most cases (38 homozygous, 8 compound heterozygous). Four novel mutations were identified (p.N252K, p.V460E, p.S485F, p.N519D). No mutations were identified in the other screened genes.

CONCLUSIONS

Newborn glaucoma on the Arabian Peninsula is typically CYP1B1-related even in the setting of developmental iris abnormality. Mild iris ectropion with partial aniridia in a newborn with glaucoma suggests mutations in CYP1B1 rather than in other genes associated with anterior segment dysgenesis. On the Arabian Peninsula p.G61E mutations are the major cause of newborn glaucoma but novel CYP1B1 mutations continue to be documented. The fact that the 9% of cases that were CYP1B1-negative did not have mutations in LTBP2 suggests that there exists at least 1 additional locus for this condition.

Interaction between ERAP1 and HLA-B27 in ankylosing spondylitis implicates peptide handling in the mechanism for HLA-B27 in disease susceptibility

Ankylosing spondylitis is a common form of inflammatory arthritis predominantly affecting the spine and pelvis that occurs in approximately 5 out of 1,000 adults of European descent. Here we report the identification of three variants in the RUNX3, LTBR-TNFRSF1A and IL12B regions convincingly associated with ankylosing spondylitis (P < 5 × 10(-8) in the combined discovery and replication datasets) and a further four loci at PTGER4, TBKBP1, ANTXR2 and CARD9 that show strong association across all our datasets (P < 5 × 10(-6) overall, with support in each of the three datasets studied). We also show that polymorphisms of ERAP1, which encodes an endoplasmic reticulum aminopeptidase involved in peptide trimming before HLA class I presentation, only affect ankylosing spondylitis risk in HLA-B27-positive individuals. These findings provide strong evidence that HLA-B27 operates in ankylosing spondylitis through a mechanism involving aberrant processing of antigenic peptides.

Choreographing metastasis to the tune of LTBP

Latent Transforming Growth Factor beta (TGFβ) Binding Proteins (LTBPs) are chaperones and determinants of TGFβ isoform-specific secretion. They belong to the LTBP/Fibrillin family and form integral components of the fibronectin and microfibrillar extracellular matrix (ECM). LTBPs serve as master regulators of TGFβ bioavailability, functioning to incorporate and spatially pattern latent TGFβ at regular intervals within the ECM, and actively participate in integrin-mediated stretch activation of TGFβ in vivo. In so doing they create a highly patterned sensory system where local changes in ECM tension can be detected and transduced into focal signals. The physiological role of LTBPs in the mammary gland remains largely unstudied, however both loss and gain of LTBP expression is found in breast cancers and breast cancer cell lines. Importantly, elevated LTBP1 levels appear in two gene signatures predictive of enhanced metastatic behavior. LTBP may promote metastasis by providing the bridge between structural and signaling components of the epithelial to mesenchymal transition (EMT).

Genome-wide association study using extreme truncate selection identifies novel genes affecting bone mineral density and fracture risk

Osteoporotic fracture is a major cause of morbidity and mortality worldwide. Low bone mineral density (BMD) is a major predisposing factor to fracture and is known to be highly heritable. Site-, gender-, and age-specific genetic effects on BMD are thought to be significant, but have largely not been considered in the design of genome-wide association studies (GWAS) of BMD to date. We report here a GWAS using a novel study design focusing on women of a specific age (postmenopausal women, age 55-85 years), with either extreme high or low hip BMD (age- and gender-adjusted BMD z-scores of +1.5 to +4.0, n = 1055, or -4.0 to -1.5, n = 900), with replication in cohorts of women drawn from the general population (n = 20,898). The study replicates 21 of 26 known BMD-associated genes. Additionally, we report suggestive association of a further six new genetic associations in or around the genes CLCN7, GALNT3, IBSP, LTBP3, RSPO3, and SOX4, with replication in two independent datasets. A novel mouse model with a loss-of-function mutation in GALNT3 is also reported, which has high bone mass, supporting the involvement of this gene in BMD determination. In addition to identifying further genes associated with BMD, this study confirms the efficiency of extreme-truncate selection designs for quantitative trait association studies.

LTBP2 and CYP1B1 mutations and associated ocular phenotypes in the Roma/Gypsy founder population

Primary congenital glaucoma (PCG) is a genetically heterogeneous autosomal recessive disorder, which is an important cause of blindness in childhood. The first known gene, CYP1B1, accounts for a variable proportion of cases in most populations. A second gene, LTBP2, was recently reported in association with a syndrome, in which glaucoma is secondary to lens dislocation. We report on the molecular and clinical profile of 34 families diagnosed as PCG, all originating from the Roma/Gypsy founder population. Comprehensive sequencing analysis revealed a level of heterogeneity unusual for this population, with five CYP1B1 and one ancestral LTBP2 mutation accounting for ∼70% of patients (25 out of 37) and the remainder still unexplained. Homozygosity for the founder LTBP2 p.R299X mutation resulted in a more severe clinical phenotype and poorer outcome despite a markedly higher number of surgical interventions. The genetically homogeneous group of p.R299X homozygotes showed variable phenotypes (presumably also underlying pathogenetic mechanisms), wherein PCG proper with primary dysgenesis of the trabecular meshwork, and Marfan syndrome-like zonular disease with ectopia lentis and later onset secondary glaucoma are two extremes. The spectrum manifestations may occur in different combinations and have a different evolution even within the same sibship or a single patient. Preliminary observations on compounds with mutations in both CYP1B1-LTBP2 suggest that the observed combinations are of no clinical significance and digenic inheritance is unlikely. We provide a population genetics perspective to explain the allelic heterogeneity, comparing the history and geographic distribution of the two major founder mutations--p.R299X/LTBP2 and p.E387K/CYP1B1.

[Isolated oligodontia: a case presentation and review of the literature]

Tooth agenesis is a common developmental anomaly that appears in 2.2-10% of the general population (excluding agenesis of third molars). Congenital tooth agenesis can be either Hypodontia (agenesis of fewer than six teeth excluding third molars) or Oligodontia (agenesis of more than six teeth excluding third molars). Oligodontia can occur either as an isolated condition (non-syndromic oligodontia) or be associated with cleft lip\palate and other genetic syndromes (syndromatic oligodontia). The purpose of this article is to present an unusual case of non-syndromic oligodontia and describe the dental treatment for this condition. The patient was a 25 years old healthy male with a chief complaint of multiple teeth agenesis and TMJ dysfunction. The family history revealed that the mother, grandmother and siblings have also multiple teeth agenesis. Clinical examination revealed missing of nine teeth in the maxilla (12,13, 15,15, 17, 23, 24, 25, 27) and 10 teeth in the mandible (32, 33, 34, 35, 37, 42, 43, 44, 45, 47). The patient's dental treatment plan included preparing provisional over-dentures, orthodontic treatment and dental implants (after extractions of the deciduous teeth). In the discussion of the article the pathology and the genetics of oligodontia are reviewed.

Fibrillins and latent TGFbeta binding proteins in bovine ovaries of offspring following high or low protein diets during pregnancy of dams

The microsatellite D19S884, located in intron 55 of fibrillin-3 (FBN3) gene, associates with polycystic ovary syndrome (PCOS) in familial studies. The family of fibrillin proteins (FBN1-3), which includes latent TGF-beta binding proteins (LTBP-1 to -4), are extracellular matrix proteins. We localized and examined the expression of these proteins in the adult bovine ovaries (n=7-10 per group, average age 681 days) born to mothers fed high (13% protein per total dry weight) or a low protein diet (5%) in each of the first and second trimesters of pregnancy (n=4 groups). FBN1 and LTBP-1 and -2 were the major members expressed in the mature ovary. Each protein had a unique localization pattern but all were associated with stromal tissue including the tunica albuginea (FBN1 and LTBP-2 near surface, and FBN1 and LTBP-1 deeper in the tunica), cortical stroma (FBN1 and LTBP-1) and follicular thecal layers (FBN1 in theca interna, LTBP-1 in the inner regions of the theca externa, and LTBP-2 in the outer regions of the theca externa). No significant (P>0.05) effects of maternal diet were observed on either the localization or the levels of mRNA of any of these proteins in the tunica. Expression levels of all three FBNs were positively correlated with each other, and FBN1 and 2 were positively correlated with LTBP-2, suggesting some level of co-ordinate regulation. This is the first study to investigate the expression and localization of these genes affecting TGFbeta bioavailability in the ovary.