Developing long bones respond to surrounding tissues by trans-pairing of periosteal osteoclasts and endocortical osteoblasts.

Developing long bones alter their shape while maintaining uniform cortical thickness via coordinated activity of bone-forming osteoblasts and bone-resorbing osteoclasts at periosteal and endosteal surfaces, a process we designate trans-pairing. Two types of trans-pairing shift cortical bone in opposite orientations: peri-forming trans-pairing (peri-t-p) increases bone marrow space and endo-forming trans-pairing (endo-t-p) decreases it, via paired activity of bone resorption and formation across the cortex. Here, we focused on endo-t-p in growing bones. Analysis of endo-t-p activity in the cortex of mouse fibulae revealed osteoclasts under the periosteum compressed by muscles and expression of RANKL in periosteal cells of the cambium layer. Furthermore, mature osteoblasts were localized on the endosteum, while preosteoblasts were at the periosteum and within cortical canals. X-ray tomographic microscopy revealed the presence of cortical canals more closely associated with endo- than with peri-t-p. Sciatic nerve transection followed by muscle atrophy and unloading induced circumferential endo-t-p with concomitant spread of cortical canals. Such canals likely supply the endosteum with preosteoblasts from the periosteum under endo-t-p, allowing bone shape to change in response to mechanical stress or nerve injury.

Biallelic variants in GTF3C5, a regulator of RNA polymerase III-mediated transcription, cause a multisystem developmental disorder.

General transcription factor IIIC subunit 5 (GTF3C5) encodes transcription factor IIIC63 (TFIIIC63). It binds to DNA to recruit another transcription factor, TFIIIB, and RNA polymerase III (Pol III) to mediate the transcription of small noncoding RNAs, such as tRNAs. Here, we report four individuals from three families presenting with a multisystem developmental disorder phenotype with biallelic variants in GTF3C5. The overlapping features include growth retardation, developmental delay, intellectual disability, dental anomalies, cerebellar malformations, delayed bone age, skeletal anomalies, and facial dysmorphism. Using lymphoblastoid cell lines (LCLs) from two affected individuals, we observed a reduction in TFIIIC63 protein levels compared to control LCLs. Genome binding of TFIIIC63 protein is also reduced in LCL from one of the affected individuals. Additionally, approximately 40% of Pol III binding regions exhibited reduction in the level of Pol III occupancy in the mutant genome relative to the control, while approximately 54% of target regions showed comparable levels of Pol III occupancy between the two, indicating partial impairment of Pol III occupancy in the mutant genome. Yeasts with subject-specific variants showed temperature sensitivity and impaired growth, supporting the notion that the identified variants have deleterious effects. gtf3c5 mutant zebrafish showed developmental defects, including a smaller body, head, and eyes. Taken together, our data show that GTF3C5 plays an important role in embryonic development, and that biallelic variants in this gene cause a multisystem developmental disorder. Our study adds GTF3C5-related disorder to the growing list of genetic disorders associated with Pol III transcription machinery.

Role of TOE1 variants at the nuclear localization motif in pontocerebellar hypoplasia 7.

Biallelic TOE1 variants can cause pontocerebellar hypoplasia type 7 (PCH7), a condition characterized by pontocerebellar hypoplasia with genital abnormality. TOE1 is a 3'-exonuclese for 3'-end maturation in small nuclear RNA. TOE1 pathogenic variants have been reported at the DEDD catalytic domain and zinc finger motif. Here, we describe a PCH7 patient with novel compound heterozygous TOE1 variants and a detailed clinical course. The patient was a 3-year-old female and showed developmental delay without cerebellar ataxic behavior. Head MRI revealed delayed myelination without pontocerebellar hypoplasia at 9 months of age. Progressive pontocerebellar atrophy was prominent at follow-up MRI. Cerebral abnormalities are characteristic features of PCH7 before pontocerebellar atrophy is observed. One variant, p.Arg331*, was located at the nuclear localization motif (NLM) and partially escaped from nonsense-mediated decay. This variant affected nuclear localization in mutant expressing cells, thus, the TOE1 variant at NLM leads to TOE1 dysfunction associated with nuclear mis-localization.

GPC4 truncating variant associated with Keipert syndrome and lacrimal punctal agenesis.

Lacrimal punctal agenesis is an extremely rare condition with an unclear genetic basis. Here, we report a 3-year-old male patient harboring a hemizygous variant in glypican 4 (GPC4), which causes Keipert syndrome, who presented with complete lacrimal punctal agenesis, distinctive craniofacial features, mild developmental delay, mild intellectual disability, and autism. The craniofacial features included a prominent forehead, epicanthus, depressed and broad nasal bridge, hypoplastic columella, midface hypoplasia, tented upper lip, and low-set ears. Proband exome sequencing identified a hemizygous variant in GPC4: NM_001448.3:c.1051C > T (p.Arg351*). The GPC4 variant was inherited from his heterozygous mother; X-inactivation followed a skewed pattern in his mother. This patient demonstrated clinical features consistent with Keipert syndrome including craniofacial features, brachydactyly, broad distal phalanx, broad first toe, and mild developmental delay; however, agenesis of the lacrimal puncta has not been reported previously in Keipert syndrome. Our findings suggest that GPC4, which encodes a heparan-sulfate proteoglycan, may play an important role in lacrimal morphogenesis. Our observations also suggest that Keipert syndrome should be considered in patients with lacrimal punctal agenesis.

Noonan syndrome-like phenotype associated with an ERF frameshift variant.

Noonan syndrome is a so-called "RASopathy," that is characterized by short stature, distinctive facial features, congenital heart defects, and developmental delay. Of individuals with a clinical diagnosis of Noonan syndrome, 80%-90% have pathogenic variants in the known genes implicated in the disorder, but the molecular mechanism is unknown in the remaining cases. Heterozygous pathogenic variants of ETS2 repressor factor (ERF), which functions as a repressor in the RAS/MAPK signaling pathway, cause syndromic craniosynostosis. Here, we report an ERF frameshift variant cosegregating with a Noonan syndrome-like phenotype in a family. The proband was a 3-year-old female who presented with dysmorphic facial features, including proptosis, hypertelorism, slightly down slanted palpebral fissures, low-set posteriorly rotated ears, depressed nasal bridge, short stature, and developmental delay. Exome sequencing of the proband identified a heterozygous ERF variant [NM_006494.4: c.185del p.(Glu62Glyfs*15)]. Her mother and sister showed a similar phenotype and had the same heterozygous ERF variant. A large proportion of the previously reported patients with syndromic craniosynostosis and pathogenic ERF variants also showed characteristic features that overlap with those of Noonan syndrome. The present finding supports an association between heterozygous ERF variants and a Noonan syndrome-like phenotype.

Calcified Cartilage-Guided Identification of Osteogenic Molecules and Geometries.

Calcified cartilage digested by chondroclasts provides an excellent scaffold to initiate bone formation. We analyzed bioactive proteins and microarchitecture of calcified cartilage either separately or in combination and evaluated biomimetic osteogenic culture conditions of surface-coated micropatterning. To do so, we prepared a crude extract from porcine femoral growth plates, which enhanced in vitro mineralization when coated on flat-bottom culture dishes, and identified four candidate proteins by fractionation and mass spectrometry. Murine homologues of two candidates, desmoglein 4 (DSG4) and peroxiredoxin 6 (PRDX6), significantly promoted osteogenic activity based on in vitro mineralization and osteoblast differentiation. Moreover, we observed DSG4 and PRDX6 protein expression in mouse femur. In addition, we designed circular, triangular, and honeycomb micropatterns with 30 or 50 µm units, either isolated or connected, to mimic hypertrophic chondrocyte-sized compartments. Isolated, larger honeycomb patterns particularly enhanced osteogenesis in vitro. Mineralization on micropatterns was positively correlated with the reduction of osteoblast migration distance in live cell imaging. Finally, we evaluated possible combinatorial effects of coat proteins and micropatterns and observed an additive effect of DSG4 or PRDX6 coating with micropatterns. These data suggest that combining a bioactive surface coating with osteogenic micropatterns may recapitulate initiation of bone formation during endochondral ossification.

Chordoma cells possess bone-dissolving activity at the bone invasion front.

PURPOSE: Chordomas are malignant tumors that destroy bones, compress surrounding nerve tissues and exhibit phenotypes that recapitulate notochordal differentiation in the axial skeleton. Chordomas recur frequently, as they resist radio-chemotherapy and are difficult to completely resect, leading to repeated bone destruction and local expansion via unknown mechanisms. Here, using chordoma specimens and JHC7 chordoma cells, we asked whether chordoma cells possess bone-dissolving activity. METHODS: CT imaging and histological analysis were performed to evaluate the structure and mineral density of chordoma-invaded bone and osteolytic marker expression. JHC7 cells were subjected to immunocytochemistry, imaging of cell fusion, calcium dynamics and acidic vacuoles, and bone lysis assays. RESULTS: In patients, we found that the skull base invaded by chordoma was highly porous, showed low mineral density and contained brachyury-positive chordoma cells and conventional osteoclasts both expressing the osteolytic markers tartrate-resistant acid phosphatase (TRAP) and collagenases. JHC7 cells expressed TRAP and cathepsin K, became multinucleated via cell-cell fusion, showed spontaneous calcium oscillation, and were partly responsive to the osteoclastogenic cytokine RANKL. JHC7 cells exhibited large acidic vacuoles, and nonregulatory bone degradation without forming actin rings. Finally, bone-derived factors, calcium ions, TGF-ß1, and IGF-1 enhanced JHC7 cell proliferation. CONCLUSION: In chordoma, we propose that in addition to conventional bone resorption by osteoclasts, chordoma cells possess bone-dissolving activity at the tumor-bone boundary. Furthermore, bone destruction and tumor expansion may occur in a positive feedback loop.

A case of inherited glycosylphosphatidylinositol deficiency caused by PGAP3 variant with uniparental isodisomy on chromosome 17.

BACKGROUND: Inherited glycosylphosphatidylinositol (GPI) deficiency is an autosomal recessive disease and a set of syndromes caused by different genes involved in the biosynthesis of phosphatidylinositol characterized by severe cognitive disability, elevated serum alkaline phosphatase (ALP) levels, and distinct facial features. This report presents a patient with inherited GPI deficiency caused by a homozygous frameshift variant of PGAP3 due to uniparental isodisomy (UPiD) on chromosome 17. METHOD: Clinical characteristics of the patient were collected. Microarray analysis followed by adaptive sampling sequencing targeting chromosome 17 was used for the identification of variants. Sanger sequencing was used to confirm the variant in the target region. RESULTS: The patient was born at 38 weeks of gestation with a birthweight of 3893 g. He had a distinctive facial appearance with hypertelorism, wide nasal bridge, and cleft soft palate. Postnatal head magnetic resonance imaging revealed a Blake's pouch cyst. The serum ALP level was 940 IU/L at birth and increased to 1781 IU/L at 28 days of age. Microarray analysis revealed region of homozygosity in nearly the entire region of chromosome 17, leading to the diagnosis of UPiD. Adaptive sampling sequencing targeting chromosome 17 confirmed the homozygous variant NM_033419:c.778dupG (p.Val260Glyfs*14) in the PGAP3 gene, resulting in a diagnosis of inherited GPI deficiency. CONCLUSION: This is the first report of inherited GPI deficiency caused by UPiD. Inherited GPI deficiency must be considered in patients with unexplained hyperphosphatasemia.

General Anesthesia for Patients With Cyclic Vomiting Syndrome and Obesity: A Case Report.

Cyclic vomiting syndrome (CVS) is a chronic digestive disorder characterized by recurrent episodes of severe nausea and vomiting. The perioperative management of patients with CVS undergoing general anesthesia is challenging, especially when combined with obesity. This case report describes the successful management of a patient with CVS and obesity who underwent dental surgery under general anesthesia. A 21-year-old woman with CVS, obesity (body mass index, 35), and intellectual disability was scheduled for tooth extraction and composite resin restoration under general anesthesia. The patient was diagnosed with CVS at the age of 20 years with frequent vomiting attacks requiring hospitalization. Surgery was scheduled during the CVS remission to reduce the risk of perioperative vomiting. Preoperative laboratory test results were normal, including serum adrenocorticotropic hormone (ACTH), anti-diuretic hormone (ADH), and cortisol levels. General anesthesia was induced using remifentanil and propofol. Nasal endotracheal intubation was performed after rocuronium administration. Local anesthesia (2% lidocaine with 1:80,000 epinephrine) was used for all dental procedures. Postoperatively, midazolam was administered to control agitation. No postoperative vomiting occurred. Serum ACTH, ADH, and cortisol levels showed no significant changes before and after anesthesia, suggesting that hypothalamic-pituitary-adrenal (HPA) axis activation due to surgical stress did not occur. This case highlights the importance of careful perioperative planning and monitoring stress-related hormone levels in patients with CVS or obesity. An anesthetic approach using midazolam may effectively suppress HPA axis activation and prevent postoperative vomiting.