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.

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

LTBP1 is closely related to TGF-ß1 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-ß 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)-ß-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.

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.

[IDENTIFICATION OF A NOVEL LTBP3 GENE PATHOGENIC VARIANT IN DRUZE ARAB PATIENTS PRESENTED WITH SYNDROMIC SHORT STATURE WITH BRACHYOLMIA AND AMELOGENESIS IMPERFECTA].

BACKGROUND: Short stature is a common finding among the general population, mostly presented as an isolated phenotype. The syndromic short statute is rare and complex. Recently, we examined several patients from related families sharing both short stature and congenital dental abnormalities. OBJECTIVES: 1. Clinical characterization of syndromic short stature; 2. To find the disease mutation and evaluate the carrier state in the particular community. METHODS: Clinical characterization- by medical history, medical records and physical examination; Homozygosity mapping - by using the Single nucleotide polymorphism (SNP) chromosomal microarrays (CMA) analysis and gene mutation detection by ABI Sanger sequence. RESULTS: All patients present with short stature severe dental anomalies including enamel formation and mineralization defect, oligodontia, abnormal shape and retarded eruption. CMA analysis in 3 patients and 2 healthy members of four families was normal. One homozygote region in chromosome 11 (11p11.2- 11q13.3) was found in all patients. By using the candidate gene approach, amongst the 301 genes found within this region, only one, the LTBP3 gene (Latent Transforming Growth Factor-Beta-Binding Protein-3) has high priority for sequence. Hence, LTBP3 (OMIM-602090) pathogenic variant is responsible for "brachyolmia with amelogenesis imperfecta" also known as "Dental Anomalies and Short Stature (DASS)" (OMIM- 601216). We sequenced all 29 LTBP3 exons and a novel splice pathogenic variant, c.1346-1G>A chr11:65319629, in exon 8 was identified. The variant segregated well within healthy tested family members. We found a high carrier rate in the village (1:15). CONCLUSIONS: We identified a novel and common LTBP3 gene pathogenic variant responsible for short stature, brachyolmia and amelogenesis imperfecta in Druze Arab patients.

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.

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.

Zonule-Associated Gene Variants in Isolated Ectopia Lentis and Glaucoma.

PRCIS: We report 3 novel variants in fibrillin-1 (FBN1) and latent transforming growth factor-ß-binding protein 2 (LTBP2) in 3 families with isolated ectopia lentis (EL), which shed new light on the diagnosis and genetic counseling of EL and secondary glaucoma in clinical settings. PURPOSE: To explore the genetic mechanism in 3 families with isolated EL and secondary angle closure glaucoma. METHODS: Three Han Chinese families with EL and glaucoma were recruited. All of the participants underwent complete ocular and general physical examinations and DNA samples were extracted from peripheral venous blood and screened for disease-causing variants using whole exome and Sanger sequencing. In silico analyses were performed to predict the structural and functional changes in gene variants and abnormal proteins. RESULTS: All 3 probands presented with EL and pupillary-blocking glaucoma. Genetic testing showed that all the patients have zonule-related gene mutations, with the proband (II:1), as well as his mother (I:2) and daughters (III:1 and III:2) from family 1 carrying a heterozygous mutation in FBN1 gene (c.6493G>T:p.(V2165L)); the proband (II:1) from family 2 carrying a heterozygous mutation in FBN1 gene (c.2543C>A:p.(T848N)), and the proband (II:1) from family 3 carrying a pair of compound heterozygous mutations in LTBP2 gene (c.4825T>A:p.(C1609S) / c.529T>C:p.(W177R)). No other genetic variants were found to be associated with the phenotypes of patients and other family members in this study. All variants are predicted to affect the structure and function of proteins as risk factors for EL based on bioinformatics analysis. CONCLUSION: Four novel mutations were identified in 3 families with EL, suggesting an intimate link between specific mutations in FBN1 and LTBP2 and isolated EL and angle closure glaucoma. Our results expanded the variant spectrum of zonule-related genes and helped explore the underlying molecular pathology of these disorders.

Whole-exome screening for primary congenital glaucoma in Lebanon.

PURPOSE: Mutations were previously identified in the CYP1B1 gene in six out of 18 Lebanese families (33%) with primary congenital glaucoma (PCG). The purpose of this study is to determine the frequency and type of pathogenic mutations in other genes and compare to other populations using whole-exome sequencing and perform genotype-phenotype correlations. METHODS: Twelve PCG patients previously negative for CYP1B1/MYOC mutations were subjected to whole-exome sequencing. Targeted screening for glaucoma-associated genes was performed. Candidate variants were verified by Sanger sequencing and evaluated in family members for segregation analysis and in 100 normal controls. Clinical correlations were established as to severity of disease presentation, course, and visual outcomes. RESULTS: Six mutations in known PCG-causing genes were identified in five patients: homozygous mutations in CYP1B1 (p.R368G), LTBP2 (p.E1013G), and TEK (p.T693I), and heterozygous mutations in FOXC1 (p.Q92*), TEK (c.3201-1 G>A), ANGPT1 (p.K186N), and CYP1B1 (p.R368G). Two patients, negative for CYP1B1 in the previous study, were revealed positive in the current study, due to different sets of primers and PCR conditions. Potentially damaging variants were noted in several candidate genes. Except for FOXC1 mutations, all genetic variants described here are novel. Intra-ocular pressure and final optic nerve cup-to-disc ratio were highest in the patient with three mutations in LTBP2/TEK/ANGPT1 genes. CONCLUSION: This study provides new data on the spectrum of mutations of PCG in Lebanon. This highlights the genetic heterogeneity of the Lebanese population, noted for high rates of consanguinity in 50% in this cohort. This study emphasizes the importance of whole-exome sequencing in elucidating new candidate genes for PCG in the Lebanese.

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.

Association of EFEMP1 with juvenile-onset open angle glaucoma in a patient with concomitant COL11A1-related Stickler syndrome.

BACKGROUND: Juvenile onset open-angle glaucoma is described as a primary open-angle glaucoma, with an age of onset before 40 years. These patients have a higher prevalence of myopia. PURPOSE: We describe the phenotype of juvenile onset open-angle glaucoma in a patient with a rare variant in EFEMP1 gene, who was also detected to have Stickler syndrome(STL). METHODS: Whole exome sequencing (WES) was undertaken in 40 unrelated families where the proband had juvenile onset open-angle glaucoma (JOAG). RESULTS: Out of these, eight were autosomal dominant, while the rest did not have any other affected first-degree relative. Out of the 8 autosomal dominant JOAG families, MYOC mutations were detected in 3(37.5%) and LTBP2 in 1(12.5%). One family (12.5%) had a rare EFEMP1 sequence variant in both affected father and daughter. The daughter also had high myopia and a pathogenic COL11A1 sequence variant that led to a coincidental diagnosis of STL in her. CONCLUSIONS: This is a rare association of EFEMP1 and COL11A1 sequence variants in a JOAG patient with STL. The study also reiterates the association of JOAG with EFEMP1, which should be looked for, especially in families with autosomal dominant JOAG.

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.

Association of polymorphisms rs2303729, rs10880, and rs1131620 of LTBP4 with sarcopenia in elderly patients with type 2 diabetes mellitus.

BACKGROUND: Latent TGFß binding protein 4 (LTBP4) modifies skeletal muscle function, and polymorphisms in this gene have been associated with a longer ambulation time in patients with Duchenne muscular dystrophy. However, no studies associate these polymorphisms with an acquired muscle condition. AIM: The study aims to determine whether three functional variants within the LTBP4 were associated with sarcopenia in patients with type 2 diabetes mellitus (T2DM). SUBJECTS AND METHODS: We performed an analysis with 144 elderly individuals with T2DM, including 101 without sarcopenia and 43 with sarcopenia. Polymorphism frequency was determined by real-time PCR allelic discrimination TaqMan assay. RESULTS: Under different genetic models, the univariant analysis did not show a significant association of any polymorphism with sarcopenia. But the multivariate model analysis showed that variant rs1131620 (OR 7.852, 95% CI 1.854-33.257, p = 0.005) was significantly associated with sarcopenia under a dominant model. Under the same analysis, the variants rs2303729 and rs10880 had a more discrete association (OR 3.537 95% CI 1.078-11.607, p = 0.037; OR 5.008, 95% CI 1.120-22.399, p = 0.035, respectively). CONCLUSIONS: Our study highlights the importance of studying LTBP4 polymorphisms associated with sarcopenia. These findings suggest that the rs1131620 polymorphism of the LTBP4 may be part of the observed sarcopenia process in patients with T2DM.

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

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 TGFß. Fibrillinopathies, that can also result from mutation of these ADAMTS/L proteins, have been linked to disrupted TGFß homeostasis. ADAMTS6 and ADAMTS10 are homologous metalloproteases with poorly characterized substrates where ADAMTS10 is thought to process fibrillin-2 and ADAMTS6 latent TGFß-binding protein (LTBP)-1. In order to understand the contribution of ADAMTS6, and these other members of the ADAMTS/L family, to TGFß homeostasis, we have analyzed the effects of ADAMTS6, ADAMTS10 and ADAMTSL2 expression on TGFß activation. We found that their expression increases TGFß activation in a dose dependent manner, following stimulation with mature TGFß1. For ADAMTS6, the catalytically active protease is required for effective TGFß activation, where ADAMTS6 cleaves LTBP3 as well as LTBP1, and binds to the large latent TGFß 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 TGFß is perturbed ADAMTS6 can influence TGFß activation via two mechanisms. It directly cleaves the latent TGFß complexes and also acts indirectly, along with ADAMTS10 and ADAMTSL2, by altering the mechanotension of cells. Together this increases activation of TGFß from large latent complexes which may contribute to disease pathogenesis.

Next-generation whole exome sequencing to delineate the genetic basis of primary congenital glaucoma.

To delineate the genetic bases of primary congenital glaucoma (PCG), we ascertained a large cohort consisting of 48 consanguineous families. Of these, we previously reported 26 families with mutations in CYP1B1 and six families with LTBP2, whereas the genetic bases responsible for PCG in 16 families remained elusive. We employed next-generation whole exome sequencing to delineate the genetic basis of PCG in four of these 16 familial cases. Exclusion of linkage to reported PCG loci was established followed by next-generation whole exome sequencing, which was performed on 10 affected individuals manifesting cardinal systems of PCG belonging to four unresolved families along with four control samples consisting of genomic DNAs of individuals harboring mutations in CYP1B1 and LTBP2. The analyses of sequencing datasets failed to identify potential causal alleles in the 10 exomes whereas c.1169G > A (p. Arg390His) in CYP1B1 and c.3427delC (p.Gln1143Argfs*35) in LTBP2 were identified in the control samples. Taken together, next-generation whole exome sequencing failed to delineate the genetic basis of PCG in familial cases excluded from mutations in CYP1B1 and LTBP2. These data strengthen the notion that compound heterozygous coding variants or non-coding variants might contribute to PCG.

First characterization of LTBP3 variants in two Moroccan families with hypoplastic amelogenesis imperfecta.

OBJECTIVES: To decipher and improve the molecular diagnosis of Hypoplastic Amelogenesis Imperfecta in Morocco. DESIGN: Using whole exome sequencing, we analyzed two Moroccan families with Hypoplastic Amelogenesis Imperfecta. The 2 patients from the first family had dental anomalies and short stature syndrome, brachyolmia and nephrocalcinosis with difference in severity, while the proband of the second family had Hypoplastic Amelogenesis Imperfecta with a suspicion of brachyolmia. RESULTS: We identified two novel LTBP3 homozygous variants, the c.2495delT deletion (p.Phe832SerfsTer36) and the c.3716 G>A (p.Cys1239Tyr) missense variant, respectively. Molecular modelling and stability analyses of the missense variant disclosed a possible destabilization of the wild-type structure. CONCLUSION: Although LTBP3 variants were related to this phenotype in various populations, we report the first LTBP3 variants in the Moroccan population, in families with Hypoplastic Amelogenesis Imperfecta.

First report of a short in-frame biallelic deletion removing part of the EGF-like domain calcium-binding motif in LTBP4 and causing autosomal recessive cutis laxa type 1C.

Cutis laxa (CL) is a rare connective tissue disorder characterized by wrinkled, abundant and sagging skin, sometimes associated with systemic impairment. Biallelic alterations in latent transforming growth factor beta-binding protein 4 gene (LTBP4) cause autosomal recessive type 1C cutis laxa (ARCL1C, MIM #613177). The present report describes the case of a 17-months-old girl with cutis laxa together with a literature review of previous ARCL1C cases. Based on proband main clinical signs (cutis laxa and pulmonary emphysema), clinical exome sequencing (CES) was performed and showed a new nine base-pairs homozygous in-frame deletion in LTBP4 gene. RT-PCR and cDNA Sanger sequencing were performed in order to clarify its impact on RNA. This report demonstrates that a genetic alteration in the EGF-like 14 domain calcium-binding motif of LTBP4 gene is likely responsible for cutis laxa in our patient.