Novel TRPV4 Pathogenic Variant in Severe Metatropic Skeletal Dysplasia: A Case Report.

We report an eight-year-old girl with a novel homozygous TRPV4 gene pathogenic variant c.2355G>T p. (Trp785Cys) with mesomelic shortening, odontoid hypoplasia, multiple joint contractures, thoracolumbar kyphosis, pectus carinatum, halberd pelvis, and dumb-bell shaped long bones. The novel variant caused a severe recessive form of metatropic dysplasia.

Novel TRPV4 Pathogenic Variant in Severe Metatropic Skeletal Dysplasia: A Case Report

@#We report an eight-year-old girl with a novel homozygous TRPV4 gene pathogenic variant c.2355G>T p. (Trp785Cys) with mesomelic shortening, odontoid hypoplasia, multiple joint contractures, thoracolumbar kyphosis, pectus carinatum, halberd pelvis, and dumb-bell shaped long bones. The novel variant caused a severe recessive form of metatropic dysplasia.

Impaired neurite development and mitochondrial dysfunction associated with calcium accumulation in dopaminergic neurons differentiated from the dental pulp stem cells of a patient with metatropic dysplasia.

Transient receptor potential vanilloid member 4 (TRPV4) is a Ca2+ permeable nonselective cation channel, and mutations in the TRPV4 gene cause congenital skeletal dysplasias and peripheral neuropathies. Although TRPV4 is widely expressed in the brain, few studies have assessed the pathogenesis of TRPV4 mutations in the brain. We aimed to elucidate the pathological associations between a specific TRPV4 mutation and neurodevelopmental defects using dopaminergic neurons (DNs) differentiated from dental pulp stem cells (DPSCs). DPSCs were isolated from a patient with metatropic dysplasia and multiple neuropsychiatric symptoms caused by a gain-of-function TRPV4 mutation, c.1855C>T (p.L619F). The mutation was corrected by CRISPR/Cas9 to obtain isogenic control DPSCs. Mutant DPSCs differentiated into DNs without undergoing apoptosis; however, neurite development was significantly impaired in mutant vs. control DNs. Mutant DNs also showed accumulation of mitochondrial Ca2+ and reactive oxygen species, low adenosine triphosphate levels despite a high mitochondrial membrane potential, and lower peroxisome proliferator-activated receptor gamma coactivator 1-alpha expression and mitochondrial content. These results suggested that the persistent Ca2+ entry through the constitutively activated TRPV4 might perturb the adaptive coordination of multiple mitochondrial functions, including oxidative phosphorylation, redox control, and biogenesis, required for dopaminergic circuit development in the brain. Thus, certain mutations in TRPV4 that are associated with skeletal dysplasia might have pathogenic effects on brain development, and mitochondria might be a potential therapeutic target to alleviate the neuropsychiatric symptoms of TRPV4-related diseases.

Accelerated osteoblastic differentiation in patient-derived dental pulp stem cells carrying a gain-of-function mutation of TRPV4 associated with metatropic dysplasia.

Metatropic dysplasia (MD) is a congenital skeletal dysplasia characterized by severe platyspondyly and dumbbell-like long-bone deformities. These skeletal phenotypes are predominantly caused by autosomal dominant gain-of-function (GOF) mutations in transient receptor potential vanilloid 4 (TRPV4), which encodes a nonselective Ca2+-permeable cation channel. Previous studies have shown that constitutive TRPV4 channel activation leads to irregular chondrogenic proliferation and differentiation, and thus to the disorganized endochondral ossification seen in MD. Therefore, the present study investigated the role of TRPV4 in osteoblast differentiation and MD pathogenesis. Specifically, the behavior of osteoblasts differentiated from patient-derived dental pulp stem cells carrying a heterozygous single base TRPV4 mutation, c.1855C > T (p.L619F) was compared to that of osteoblasts differentiated from isogenic control cells (in which the mutation was corrected using the CRISPR/Cas9 system). The mutant osteoblasts exhibited enhanced calcification (indicated by intense Alizarin Red S staining), increased intracellular Ca2+ levels, strongly upregulated runt-related transcription factor 2 and osteocalcin expression, and increased expression and nuclear translocation of nuclear factor-activated T cell c1 (NFATc1) compared to control cells. These results suggest that the analyzed TRPV4 GOF mutation disrupts osteoblastic differentiation and induces MD-associated disorganized endochondral ossification by increasing Ca2+/NFATc1 pathway activity. Thus, inhibiting the NFATc1 pathway may be a promising potential therapeutic strategy to attenuate skeletal deformities in MD.

Metatropic Dysplasia of Nonlethal Variant in a Chinese Child - A Case Report.

Metatropic dysplasia (MD), is a rare skeletal dysplasia occurring predominantly in infants characterized by a distinctive long torso and short limbs; it is as a result of mutations in the TRPV4 gene. However, a clear distinction between various forms of skeletal dysplasias caused by the transient receptor potential vanilloid 4 (TRPV4) gene is difficult but could be achieved by a combination of gene sequencing, medical and radiological criteria. We hereby report a case of a 14-month old girl who presented with an abnormal stature. The diagnosis of nonlethal MD was confirmed by X-ray with dumbbell-shaped long bones, platyspondyly, and delayed carpal ossification, as well as broadened pelvis with marginally widened ilia, epiphyseal plates, and slightly flattened acetabula. Furthermore, gene sequencing confirmed gene mutation on exon 15 of the TRPV4 gene with a heterozygous missense mutation (c.2396C > T), but no mutation was present in her parents. Our findings recorded metatropic dysplasia with the c.2396C > T mutation in the TRPV4 gene in China. This mutation caused changes in amino acid of TRPV4, which can induce growth retardation in children.

Novel gain-of-function mutation of TRPV4 associated with accelerated chondrogenic differentiation of dental pulp stem cells derived from a patient with metatropic dysplasia.

Metatropic dysplasia is a congenital skeletal dysplasia characterized by severe platyspondyly, dumbbell-like deformity of long tubular bones, and progressive kyphoscoliosis with growth. It is caused by mutations in the gene TRPV4, encoding the transient receptor potential vanilloid 4, which acts as a calcium channel. Many heterozygous single base mutations of this gene have been associated with the disorder, showing autosomal dominant inheritance. Although abnormal endochondral ossification has been observed by histological examination of bone in a patient with lethal metatropic dysplasia, the etiology of the disorder remains largely unresolved. As dental pulp stem cells (DPSCs) are mesenchymal stem cells that differentiate into bone lineage cells, DPSCs derived from patients with congenital skeletal dysplasia might be useful as a disease-specific cellular model for etiological investigation. The purpose of this study was to clarify the pathological association between TRPV4 mutation and chondrocyte differentiation by analyzing DPSCs from a patient with non-lethal metatropic dysplasia. We identified a novel heterozygous single base mutation, c.1855C>T in TRPV4. This was predicted to be a missense mutation, p.L619F, in putative transmembrane segment 5. The mutation was repaired by CRISPR/Cas9 system to obtain isogenic control DPSCs for further analysis. The expression of stem cell markers and fibroblast-like morphology were comparable between patient-derived mutant and control DPSCs, although expression of TRPV4 was lower in mutant DPSCs than control DPSCs. Despite the lower TRPV4 expression in mutant DPSCs, the intracellular Ca2+ level was comparable at the basal level between mutant and control DPSCs, while its level was markedly higher following stimulation with 4α-phorbol 12,13-didecanoate (4αPDD), a specific agonist for TRPV4, in mutant DPSCs than in control DPSCs. In the presence of 4αPDD, we observed accelerated early chondrocyte differentiation and upregulated mRNA expression of SRY-box 9 (SOX9) in mutant DPSCs. Our findings suggested that the novel missense mutation c.1855C>T of TRPV4 was a gain-of-function mutation leading to enhanced intracellular Ca2+ level, which was associated with accelerated chondrocyte differentiation and SOX9 upregulation. Our results also suggest that patient-derived DPSCs can be a useful disease-specific cellular model for elucidating the pathological mechanism of metatropic dysplasia.

The Management of Kyphosis in Metatropic Dysplasia.

DESIGN: Retrospective review. OBJECTIVE: To describe the presentation and progression, and compare treatments of severe thoracic kyphosis in a cohort of patients with metatropic dysplasia. SUMMARY OF BACKGROUND DATA: Metatropic dysplasia is a rare skeletal dysplasia characterized by several abnormalities, including severe platyspondyly and vertebral wedging. These lead to marked kyphoscoliosis that begins in the first year of life and progresses to a stiff, short thorax and restrictive lung disease. There is no study that specifically addresses treatment of kyphosis in this cohort. METHODS: A 12-year retrospective chart review at a single institution was performed to identify metatropic dysplasia patients. Comparison between four main treatment groups-observation, bracing, anterior release and growing construct, and anterior release and final fusion-were made radiographically with regard to thoracolumbar, T2-T12, and major Cobb kyphosis; sagittal vertical alignment; and C7-kyphosis apex distance, taken at presentation, pre- and posttreatment, and final follow-up. RESULTS: Twenty patients with metatropic dysplasia presented at an average age of 3.1 years with a kyphosis of 75°, and were followed an average of 8.5 years. Those treated surgically presented with an average of 86.7° kyphosis, 88 mm C7-kyphosis apex distance, and 50 mm positive sagittal vertical alignment (SVA). Postsurgical reduction of kyphosis averaged 43° with less than 4° loss of correction in all groups except the constructs involving rib fixation. Recent use of staged thoracoscopic anterior soft tissue release, halo traction, and growing rod construct has produced the most dramatic results with average kyphosis correction of 71° and evidence of anterior bony remodeling. In those treated with observation, kyphosis progressed less than a quarter degree per year. CONCLUSIONS: Thoracic kyphosis in metatropic dysplasia does not uniformly progress in all patients and therefore can be initially observed. In those who progress, several surgical options exist including growth-friendly constructs that have demonstrated success without a higher rate of complications. LEVEL OF EVIDENCE: Level IV.

Novel TRPV4 variant causes a severe form of metatropic dysplasia.

We present a girl born with a frontal bossing, short neck, bell-shaped thorax, short limbs with prominent joints, and a tail-like coccygeal appendage. Genetic screening of TRPV4 identified a novel de novo heterozygous missense variant. We believe the variant causes the severe form of metatropic dysplasia in this patient.

Characteristic Diagnostic Clues of Metatropic Dysplasia: The Lumbothoracic Humpback with Dumbbell Appearance of the Long Bones.

Metatropic dysplasia (MD) is a rare skeletal dysplasia associated with heterozygous mutations in the TRPV4 gene. We describe a 28-month-old boy with knock-knees referred for metabolic investigation suspected of carrying vitamin D-resistant rickets. He has received regular vitamin D prophylaxis at the usual dose. Laboratory investigations revealed normal values for calcium, phosphorus and alkaline phosphatase. He was short (-3.5 SDS), his mental development was normal, and he started to walk at the age of 22 months. The diagnostic clue for the diagnosis of metatropic dysplasia was the presence of the hump back in the upper lumbar and lower thoracic vertebrae, in addition to a long and narrow chest. An X-ray survey of the skeleton revealed platyspondyly, dysplastic metaphyses with dumbbell appearance of the long bones, kyphoscoliosis, and narrow and elongated thorax with short ribs. This is the first patient with MD in the Republic of Macedonia. Knock-knees were the cause of his referral, as a peculiarity of his phenotype. The very presence of the hump back, and the dumbbell appearance of the long bones distinguished the MD from other bone dysplasias with similar characteristics. We believe that the presence of those two features can shorten the path to accurate diagnosis in the crowded field of overlapping skeletal dysplasias. The diagnosis of MD in this patient was further confirmed by the discovery of the mutation c.2396C>T; p.Pro799Leu (P799L) of the TRPV4 gene.

Metatropic dysplasia in third trimester of pregnancy and a novel causative variant in the TRPV4 gene.

Prenatal diagnosis of skeletal dysplasias is particularly difficult for many reasons and differentiating these disorders in the prenatal period can be challenging because they are rare and many of the ultrasound findings are not necessarily pathognomonic for a specific disorder. The diagnosis is often made just after birth or exitus. The prenatal diagnosis of osteochondrodysplasias is based predominantly upon fetal ultrasound findings and it focuses substantially on the possible lethality of the disorder, without always being able to find a specific name for the disorder. Metatropic dysplasia is a rare osteochondrodysplasia due to mutations in the TRPV4 gene: TRPV4 is a cation channel, non-selectively permeable to calcium, encoded by a gene on chromosome 12q24.11; it is widely expressed and involved in many different physiological processes through responses to several different stimuli (physical, chemical, and hormonal) in ciliated epithelial cells. The exact incidence of this disorder is not known, however less than a hundred cases have been reported at present, with only two prenatal reports but without any reference to the molecular test. We describe the first report of molecular diagnosis of metatropic dysplasia carried out in prenatal diagnosis: the molecular testing of the TRPV4 (transient receptor potential cation channel, subfamily V, member 4, MIM *605427) gene in our case, in fact, detected a causative variant, confirming the diagnostic suspicion, which was made possible thanks also to the utilization of MRI and CT scan. In our case different imaging methods together with the close cooperation of a multidisciplinary team and test availability, allowed an accurate diagnosis.

Metatropic dysplasia-a skeletal dysplasia with challenging airway and other anesthetic concerns.

BACKGROUND: Metatropic dysplasia is a rare form of skeletal dysplasia requiring multiple anesthetics for surgical and imaging procedures, most of which are orthopedic procedures. We provide centralized care to patients with skeletal dysplasia at our tertiary care pediatric hospital, and we were able to collect the largest number of metatropic dysplasia patients reported to date. AIM: The aim of this retrospective study was to describe and characterize the anesthetic difficulties in this high-risk population. METHODS: Medical charts of all patients with metatropic dysplasia were reviewed to collect data, including anesthetics performed, difficulties, and complications related to the anesthetic care, co-morbid conditions, and related events. RESULTS: Twenty-three patients with metatropic dysplasia underwent 188 anesthetics with 61% of the anesthetics having been administered for orthopedic procedures. Fourteen of 23 (60.8%) progressively became difficult to intubate over the course of their care, with 12 out of 14 having undergone cervical spine fusion. These 14 patients had a total of 133 procedures. Sixty procedures (45.1%) had an airway described as difficult. Glidescope was the difficult airway tool most commonly used (68%) with flexible fiberoptic scope used 12% and Miller or Macintosh blade used 18% of the time. In addition to the airway difficulties, spinal canal narrowing or stenosis was widely prevalent, and no neuraxial anesthetic was performed in any of our patients. CONCLUSION: Difficult airway is the most common co-morbid condition present in patients with metatropic dysplasia, especially if their cervical spine has been fused. Familiarity with the difficulties involving the airway and its management is critical in safe and successful management of anesthesia in this high-risk population.

Somatic mosaicism for a lethal TRPV4 mutation results in non-lethal metatropic dysplasia.

Dominant mutations in TRPV4, which encodes the Transient Receptor Potential Cation Channel Subfamily V Member 4 calcium channel, result in a series of musculoskeletal disorders that include a set of peripheral neuropathies and a broad phenotypic spectrum of skeletal dysplasias. The skeletal phenotypes range from brachyolmia, in which there is scoliosis with mild short stature, through perinatal lethal metatropic dysplasia. We describe a case with phenotypic findings consistent with metatropic dysplasia, but in whom no TRPV4 mutation was detected by Sanger sequence analysis. Exome sequence analysis identified a known lethal metatropic dysplasia mutation, TRPV4L618P , which was present at lower frequency than would be expected for a heterozygous change. The affected individual was shown to be a somatic mosaic for the mutation, providing an explanation for the milder than expected phenotype. The data illustrate that high-throughput sequencing of genomic DNA can facilitate detection of mosaicism with higher sensitivity than Sanger sequence analysis and identify a new genetic mechanism for metatropic dysplasia. © 2016 Wiley Periodicals, Inc.

Clinical and genetic study on a family with metatropic dysplasia due to transient receptor potential vanilloid 4 gene mutation / 中华实用儿科临床杂志

Objective To summarize the clinical,radiographic and genetic features of a family with metatropic dysplasia,in order to improve the level of understanding and diagnosis of this disease.Methods The proband,a one-year old boy,was diagnosed as metatropic dysplasia.His mother was 26 years old with mildly phenotype.Their clinical features and bone X-ray findings were analyzed.The DNA samples of the proband and his parents were collected.The coding exons and flanking introns regions of transient receptor potential vanilloid 4 (TRPV4) gene were amplified by polymerase chain reaction (PCR) and analyzed by DNA automatic detector.The pathology,diagnosis,treatment and prognosis were expounded.Results The symptoms of the boy were characterized by short extremities,a short trunk with progressive kyphoscoliosis,and craniofacial abnormalities that include a prominent forehead,midface hypoplasia,and a squared-off jaw.His motor development was slightly delayed.Mental development was normal.Bone X ray of the boy showed platyspondyly and severe metaphyseal enlargement with shortening of long bones and irregularities and delayed ossification of epiphysis.The patient and his mother were heterozygous for the nucleotide substitutions c.2396 ＞ T (p.P799L) in TRPV4 gene.Conclusions The patient and his mother with metatropic dysplasia were diagnosed with TRPV4 gene analysis.The patient showed typical clinical features.His mother was mild.Metatropic dysplasia had significantly clinical heterogeneity.Gene analysis is helpful for the diagnosis.

A mutation in TRPV4 results in altered chondrocyte calcium signaling in severe metatropic dysplasia.

Transient receptor potential cation channel, subfamily V, member 4 (TRPV4) is a polymodal modulated non-selective cation channel required for normal development and maintenance of bone and cartilage. Heterozygous mutations of this channel cause a variety of channelopathies, including metatropic dysplasia (MD). We analyzed the effect of a novel TRPV4 mutation c.2398G>A, p.Gly800Asp on intracellular calcium ([Ca(2+) ]i ) regulation in chondrocytes and compared this response to chondrocytes with a frequently observed mutation, c.2396C>T, p.Pro799Leu. We observed temperature-dependent [Ca(2+) ]i oscillations in both intact and MD chondrocytes however, MD mutations exhibited increased peak magnitudes of [Ca(2+) ]i during oscillations. We also found increased baseline [Ca(2+) ]i in MD primary cells, as well as increased [Ca(2+) ]i response to either hypotonic swelling or the TRVP4-specific agonist, GSK1016790A. Oscillations and stimulation responses were blocked with the TRPV4-specific antagonist, GSK205. Analysis of [Ca(2+) ]i response kinetics showed that MD chondrocytes had increased frequency of temperature-sensitive oscillations, and the magnitude and duration of [Ca(2+) ]i responses to given stimuli. Duration of the response of the p.Gly800Asp mutation to stimulation was greater than for the p.Pro799Leu mutation. These experiments show that this region of the channel is essential for proper [Ca(2+) ]i regulation. These studies of primary cells from patients show how both mutant and WT TRPV4 channels regulate cartilage and bone development. © 2015 Wiley Periodicals, Inc.

Displasia metatrópica en una niña con mutación c. 1811_1812delinsAT en el exón 11 del gen TRPV4 no informada previamente / Metatropic dysplasia in a girl with c. 1811_1812delinsAT mutation in exon 11 of the TRPV4 gene not previously reported

La displasia metatrópica es una alteración esquelética con heterogeneidad clínica, caracterizada por dismorfias craneofaciales, que incluyen prominencia frontal e hipoplasia medio facial, tronco corto con cifoescoliosis progresiva y acortamiento de las extremidades. El gen TRPV4 se localiza en 12q24.11; codifica a un canal de catión con permeabilidad no selectiva al calcio, el cual se expresa y participa en muchos procesos fisiológicos en respuesta a diversos estímulos. Más de 50 mutaciones en TRPV4 han sido descritas. Se presenta el caso de una niña de 7 meses de edad con mutación heterocigota c.1811_1812delinsAT; p.I604N en el intrón 11 no informada previamente en el gen TRPV4 y con hallazgos clínicos compatibles con displasia metatrópica.

Metatropic dysplasia is a skeletal disorder with clinical heterogeneity, characterized by craniofacial dysmorphy including frontal bossing and midface hypoplasia, short trunk, progressive kyphoscoliosis and shortened limbs. The TRPV4 gene is located on 12q24.11, coding a cation channel with non-selective permeability to calcium; it is expressed and involved in many physiological processes through responses to different stimuli. Over 50 mutations in TRPV4 have been described. We present a seven months old girl with heterozygous mutation c.1811_1812delinsAT; p.I604N in intron 11 not previously reported in the TRPV4 gene and with clinical findings compatible with metatropic dysplasia

Displasia metatrópica en una niña con mutación c.1811_1812delinsAT en el exón 11 del gen TRPV4 no informada previamente / Metatropic dysplasia in a girl with c.1811_1812delinsAT mutation in exon 11 of the TRPV4 gene not previously reported

La displasia metatrópica es una alteración esquelética con heterogeneidad clínica, caracterizada por dismorfias craneofaciales, que incluyen prominencia frontal e hipoplasia medio facial, tronco corto con cifoescoliosis progresiva y acortamiento de las extremidades. El gen TRPV4 se localiza en 12q24.11; codifica a un canal de catión con permeabilidad no selectiva al calcio, el cual se expresa y participa en muchos procesos fisiológicos en respuesta a diversos estímulos. Más de 50 mutaciones en TRPV4 han sido descritas. Se presenta el caso de una niña de 7 meses de edad con mutación heterocigota c.1811_1812delinsAT; p.I604N en el intrón 11 no informada previamente en el gen TRPV4 y con hallazgos clínicos compatibles con displasia metatrópica.(AU)

Displasia metatrópica en una niña con mutación c.1811_1812delinsAT en el exón 11 del gen TRPV4 no informada previamente / Metatropic dysplasia in a girl with c.1811_1812delinsAT mutation in exon 11 of the TRPV4 gene not previously reported

La displasia metatrópica es una alteración esquelética con heterogeneidad clínica, caracterizada por dismorfias craneofaciales, que incluyen prominencia frontal e hipoplasia medio facial, tronco corto con cifoescoliosis progresiva y acortamiento de las extremidades. El gen TRPV4 se localiza en 12q24.11; codifica a un canal de catión con permeabilidad no selectiva al calcio, el cual se expresa y participa en muchos procesos fisiológicos en respuesta a diversos estímulos. Más de 50 mutaciones en TRPV4 han sido descritas. Se presenta el caso de una niña de 7 meses de edad con mutación heterocigota c.1811_1812delinsAT; p.I604N en el intrón 11 no informada previamente en el gen TRPV4 y con hallazgos clínicos compatibles con displasia metatrópica.(AU)

Mice expressing mutant Trpv4 recapitulate the human TRPV4 disorders.

Activating mutations in transient receptor potential vanilloid family member 4 (Trpv4) are known to cause a spectrum of skeletal dysplasias ranging from autosomal dominant brachyolmia to lethal metatropic dysplasia. To develop an animal model of these disorders, we created transgenic mice expressing either wild-type or mutant TRPV4. Mice transgenic for wild-type Trpv4 showed no morphological changes at embryonic day 16.5 but did have a delay in bone mineralization. Overexpression of a mutant TRPV4 caused a lethal skeletal dysplasia that phenocopied many abnormalities associated with metatropic dysplasia in humans, including dumbbell-shaped long bones, a small ribcage, abnormalities in the autopod, and abnormal ossification in the vertebrae. The difference in phenotype between embryos transgenic for wild-type or mutant Trpv4 demonstrates that an increased amount of wild-type protein can be tolerated and that an activating mutation of this protein is required to produce a skeletal dysplasia phenotype.

A case of metatropic dysplasia: operative treatment of severe kyphoscoliosis and limb deformities.

Metatropic dysplasia is a rare but severe spondyloepimetaphyseal dysplasia characterized by long trunk and short extremities. The exact incidence is not known; however, 81 cases have been reported in the literature till now. Due to progressive kyphoscoliosis, there is a reversal of proportions in childhood (shortening of trunk with relative long extremities). The diagnostic radiographic findings include marked platyspondyly (wafer-thin vertebral bodies), widened metaphyses (dumbbell-shaped tubular bones) and small epiphysis and a specific pelvic shape. The severe kyphoscoliosis is relentless and resistant to conservative treatment with bracing. Operative treatment is controversial due to the recurrence of deformity despite aggressive correction. We, herein report a case of this rare dysplasia and its follow-up after corrective surgery for spine and limb deformity. The excellent correction and good functional pulmonary status at 6-year follow-up has never been previously reported.

A Newborn with Lethal Metatropic Dysplasia

Metatropic dysplasia is a rare spondylo epi metaphyseal dysplasia characterized by progressive kyphoscoliosis, short limbs with relatively large hands and feet and limited of motion and enlargement of the large joints. It is diagnosed based on the characteristic clinical and radiological features. Even though benign cases of this disease are frequently reported, metatropic dysplasia can often have a fatal outcome. We describe a sporadic case of the well-delineated lethal metatropic dysplasia.