Phenotypic heterogeneity in individuals with MECOM variants in 2 families

MECOM encodes the transcriptional regulators, EVI1 and MDS1-EVI1, from two distinct transcription start sites. EVI1 plays important roles in hematopoiesis and stem cell self-renewal. Recently, our group and others revealed that individuals with MECOM variants present diverse hematological and skeletal defects, including radioulnar synostosis (RUS). In the present study, we analyzed two families suspected with MECOM-associated syndrome. In family 1, a MECOM splicing variant (c.2285+1G>A) was identified in an individual with bone marrow failure (TRS4) without RUS and her mother, who had mild leukocytopenia, thrombocytopenia, and bilateral RUS. A copy neutral loss of heterozygosity decreasing the variant allele frequency was observed in the bone marrow of TRS4 and the peripheral blood leukocytes of her mother. However, TRS4 remained transfusion-dependent. In family 2, a MECOM variant (c.2208-4A>G), which was predicted to cause a cryptic acceptor site that results in a 3-base insertion (an insertion of Ser) in the mRNA, was identified in the proband, with bone marrow failure; this variant was also observed in her brother and father, both of whom have skeletal malformations, but no cytopenia. RT-PCR using leukocytes revealed a transcript with a 3-bp insertion in the proband, her brother, and the father, suggesting that the transcript variant with a 3-bp insertion is independent of blood phenotype. Collectively, these results suggest the presence of intrafamilial clinical heterogeneity in both families with MECOM splicing variants. Somatic genetic event may complicate the understanding of clinical variability among family members.

EXTH-70. ESTABLISHMENT OF INTRAVENTRICULAR SHH INHIBITION AS A THERAPEUTIC OPTION IN YOUNG PATIENTS WITH MEDULLOBLASTOMA

Medulloblastoma is the most common malignant brain tumor in children. The embryonal tumor arises in the posterior fossa and disseminates via the cerebrospinal fluid. Medulloblastoma divides in four molecular subgroups, one of which is characterized by mutations in the sonic-hedgehog (SHH) -pathway. SHH inhibition provides an elegant way of targeted therapy. The small molecule Vismodegib allosterically inhibits Smoothened (SMO), an upstream activator of SHH. Unfortunately, Vismodegib has shown to cause irreversible premature epiphyseal growth plate fusions in preclinical studies and clinical trials, preventing its systemic application in children (Kimura et al. 2008; Robinson et al. 2017). We established an intraventricular therapy with Vismodegib, combining the benefits of targeted drug delivery and minimizing systemic side effects. In a mouse model for SHH medulloblastoma, we compare intraventricular, oral and placebo treatment regarding effects on survival, tumor biology, and bone morphology. Math1-cre::Ptch1 Fl/Fl mice show a homozygous loss of PTCH1 in Math1-positive cells, resulting in SHH-pathway overactivation and development of SHH medulloblastomas. At postnatal day 11-13, Math1-cre::Ptch1 Fl/Fl mice were randomized in four treatment arms: group A (n= 9) received placebo intrathecally, B (n= 9) received Vismodegib 200 mg/kd/d orally, C (n= 19) received Vismodegib 0.2 mg/kg/d intrathecally, and D (n= 8) received Vismodegib 1.6 mg/kg/d intrathecally. Kaplan-Meier survival analysis showed a significant survival benefit for 1.6 mg/kg/d intraventricular Vismodegib compared to placebo (p= 0.012). Bone histology and X-ray analysis of intraventricular treated mice showed intact femoral and tibial growth plates, in contrast to orally treated mice that developed skeletal malformations. Further analyses such as DNA sequencing, gene expression analysis, and histological evaluation are ongoing and will add to the picture of the anti-tumor effects of intraventricular SHH-inhibition. Based on the preliminary experimental results, we conclude that intrathecal application of a SMO-inhibitor might evolve as a promising new way of targeted treatment of SHH medulloblastomas.

Insights into the Regulation of Ciliary Disassembly

The primary cilium, an antenna-like structure that protrudes out from the cell surface, is present in most cell types. It is a microtubule-based organelle that serves as a mega-signaling center and is important for sensing biochemical and mechanical signals to carry out various cellular processes such as proliferation, migration, differentiation, and many others. At any given time, cilia length is determined by a dynamic balance of cilia assembly and disassembly processes. Abnormally short or long cilia can cause a plethora of human diseases commonly referred to as ciliopathies, including, but not limited to, skeletal malformations, obesity, autosomal dominant polycystic kidney disease, retinal degeneration, and bardet-biedl syndrome. While the process of cilia assembly is studied extensively, the process of cilia disassembly and its biological role(s) are less well understood. This review discusses current knowledge on ciliary disassembly and how different cellular processes and molecular signals converge to carry out this process. This information will help us understand how the process of ciliary disassembly is regulated, identify the key steps that need further investigation, and possibly design therapeutic targets for a subset of ciliopathies that are causally linked to defective ciliary disassembly.

Oral ulceration in Stüve-Wiedemann syndrome: a new presentation

Stüve-Wiedemann syndrome (SWS) is a rare, autosomal recessive disorder, causing dysautonomia and multisystem failure. Symptoms include skeletal malformations, restricted joint mobility and desensitisation to pain. Patients with SWS presenting with intraoral lesions are extremely rare and this is probably due to their shortened lifespan. We present a case of a 9-month-old patient who presented to our Oral and Maxillofacial Surgery (OMFS)Unit with a chronic inflamed ulcer affecting the tongue, secondary to trauma from erupting central incisors. We believe that depapillation in conjunction with an increased pain threshold contributed to its development. The patient was successfully treated by extraction of the lower central incisors and intralesional steroid injections under general anaesthetic. This case highlights that patients with SWS can present to the OMFS clinician with oral lesions and that they can be safely managed under general anaesthesia.

Anesthetic management of a patient with Freeman-Sheldon syndrome undergoing oral surgery: A case report

Freeman-Sheldon syndrome (FSS) is characterized by multiple joint contractures, characteristic facial features, such as microtia, defects of the hands and feet, such as clubfoot, and skeletal malformations. This report illustrates the case of a patient with FSS who was managed under local anesthesia with intravenous sedation for oral surgery.

Congenital heart defects and skeletal malformation syndrome with congenital hemiplegia

Congenital heart defects and skeletal malformation syndrome is very rare syndrome. Most of the patients had germline mutations in ABL1 gene. A 30-year-old gentleman presented with history of congenital heart disease (ventricular septal defect) and skeletal malformations which are typical of CHDSKM. Patient also had congenital hemiplegia which is rare in CHDSKMS. Patient also had lactose intolerance since childhood. Patients were evaluated thoroughly to rule out other causes. Current report is one of the rare case reports of CHDSKMS, only few case reports have been published till now.

Congenital skeletal malformations induced by lambda-cyhalothrin, dibenzalacetone and heptanone derivatives in embryos of albino mice

Background: Insecticides such as lambda-cyhalothrin(LCT), dibenzalacetone (DBA) and heptanone HD are teratogenic substances. Skeleton is one of the organs sensitive to teratogens during the period of organogenesis. Material and methods:This study was conducted on fifty adult female albino mice, divided randomly into four groups: Group I (control group, n= 5 received corn oil orally in adose of 10 mg /kg body weight), group II (LCT group, n=10 received LCT (nano 8%)10, 20 mg /kg body weight for each subgroup), group III (DBA group, n=20, received DBA (main) 10, 20 mg /kg body weight and DBA (nano 8%)) 10,20mg /kg body weight for each subgroup) and group IV (HD group, n=15, received HD (main) 10 mg /kg body weight and HD (nano 8%)) 10,50mg /kg body weight for each subgroup),The calculated treatment dissolved in 1 ml of corn oil by orogastric tube was given to the pregnant mice during the first week of pregnancy (1st, 3rd and 5th day).The delivered live and dead pups were examined externally, then double stained and prepared for skeletal examination by dissecting microscope. Results: All experimental groups showed various anomalies that can be categorized as the following: 1) presence of dead pups and resorption sites 2) macroscopic anomalies in the form of anencephaly, extended forelimb, cranioshisis, macroglossia, lowset ears, lage eye bulge, half body, amelia, internal rotation of forelimb and encephalocele. 3) skeletal anomalies by double staining of fetal skeleton showed incomplete ossification of nasal and interparietal bones, open arch of atlas, incomplete ossification of vertebrae, supernumerary ribs, wavy ribs, incomplete ossification of ribs and sternebrae, incomplete ossification of sternum, incomplete ossification of 5th metacarpal and terminal phalangal bones and incomplete ossification of tarsal , and phalangal bones. Conclusion: Lambda-cyhalothrin, dibenzalacetone and derivatives of heptanone result in numbers of congenital gross and skeletal abnormalities that indicate their teratogenic effect. KEY WORDS: Lambada, Congenital, Skeletal, Dibenzalacetone, Heptanone, Teratogenic.

Spondylocarpotarsal synostosis syndrome due to a novel loss of function FLNB variant: a case report

Background Loss of function or gain of function variants of Filamin B (FLNB) cause recessive or dominant skeletal disorders respectively. Spondylocarpotarsal synostosis syndrome (SCT) is a rare autosomal recessive disorder characterized by short stature, fused vertebrae and fusion of carpal and tarsal bones. We present a novel FLNB homozygous pathogenic variant and present a carrier of the variant with short height. Case presentation We describe a family with five patients affected with skeletal malformations, short stature and vertebral deformities. Exome sequencing revealed a novel homozygous frameshift variant c.2911dupG p.(Ala971GlyfsTer122) in FLNB, segregating with the phenotype in the family. The variant was absent in public databases and 100 ethnically matched control chromosomes. One of the heterozygous carriers of the variant had short stature. Conclusion Our report expands the genetic spectrum of FLNB pathogenic variants. It also indicates a need to assess the heights of other carriers of FLNB recessive variants to explore a possible role in idiopathic short stature.