Functional analysis of POLD1 p.ser605del variant: the aging phenotype of MDPL syndrome is associated with an impaired DNA repair capacity.

Mandibular hypoplasia, Deafness and Progeroid features with concomitant Lipodystrophy define a rare systemic disorder, named MDPL Syndrome, due to almost always a de novo variant in POLD1 gene, encoding the DNA polymerase δ. We report a MDPL female heterozygote for the recurrent p.Ser605del variant. In order to deepen the functional role of the in frame deletion affecting the polymerase catalytic site of the protein, cellular phenotype has been characterised. MDPL fibroblasts exhibit in vitro nuclear envelope anomalies, accumulation of prelamin A and presence of micronuclei. A decline of cell growth, cellular senescence and a blockage of proliferation in G0/G1 phase complete the aged cellular picture. The evaluation of the genomic instability reveals a delayed recovery from DNA induced-damage. Moreover, the rate of telomere shortening was greater in pathological cells, suggesting the telomere dysfunction as an emerging key feature in MDPL. Our results suggest an alteration in DNA replication/repair function of POLD1 as a primary pathogenetic cause of MDPL. The understanding of the mechanisms linking these cellular characteristics to the accelerated aging and to the wide spectrum of affected tissues and clinical symptoms in the MDPL patients may provide opportunities to develop therapeutic treatments for progeroid syndromes.

Phenotypic presentations of Hajdu-Cheney syndrome according to age - 5 distinct clinical presentations.

We present five Danish individuals with Hajdu-Cheney syndrome (HJCYS) (OMIM #102500), a rare multisystem skeletal disorder with distinctive facies, generalised osteoporosis and progressive focal bone destruction. In four cases positive genetic screening of exon 34 of NOTCH2 supported the clinical diagnosis; in one of these cases, mosaicism was demonstrated, which, to our knowledge, has not previously been reported. In one case no genetic testing was performed since the phenotype was definite, and the diagnosis in the mother was genetically confirmed. The age of the patients differs widely from ten to 57 years, allowing a natural history description of the phenotype associated with this ultra-rare condition. The evolution of the condition is most apparent in the incremental bone loss leading to osteoporosis and the acro-osteolysis, both of which contribute significantly to disease burden.

Palmoplantar keratoderma, oral involvement, and homozygous CTSC mutation in two brothers from Cambodia.

Haim-Munk syndrome (HMS) and Papillon-Lefevre syndrome (PLS) are phenotypic variants of palmoplantar keratoderma (PPK) with progressive early-onset periodontitis and dental caries. HMS and PLS have been associated with homozygous or compound heterozygous mutations in the lysosomal protease gene Cathepsin C (CTSC). There have been only a few documented cases of CTSC mutations in patients from South-East Asia. We report the clinical findings of two Cambodian brothers who presented with diffuse, demarcated PPK with transgrediens extending to the elbows and knees, as well as pachyonychia and dental caries. Arachnodactyly and periodontitis were also found in the older brother. Next-generation sequencing unveiled a homozygous missense variant in CTSC (NM_001814.5: c.1337AC: p.(Asp446Ala)) in both brothers. Both parents were heterozygous for the variant, while an unaffected older brother was homozygous for the wild-type allele. Our study adds to the spectrum of mutations and associated clinical presentations for this rare genodermatosis.

Distal radius and tibia bone microarchitecture impairment in female patients with diffuse systemic sclerosis.

Radius and tibia bone microarchitecture, analyzed through a high-resolution peripheral quantitative computed tomography, were significantly impaired in female patients with diffuse systemic sclerosis compared with healthy controls. Acroosteolysis, quality of life-grip strength, hand disability, and disease duration were significantly associated with this bone deterioration. INTRODUCTION: The effect of diffuse systemic sclerosis (dSSc) on the bone is not completely understood. The objective of this study was to analyze the volumetric bone mineral density (vBMD), microarchitecture, and biomechanical parameters at the distal radius and tibia using high-resolution peripheral quantitative computed tomography (HR-pQCT, XtremeCT) in female patients with dSSc and identify clinical and laboratory variables associated with these parameters. METHODS: Thirty-eight women with dSSc and 76 healthy controls were submitted to HR-pQCT at the distal radius and tibia. Clinical and laboratory findings, bone mineral density(BMD), nailfold capillaroscopy (NC), total passive range of motion(ROM), and quality of life (health assessment questionnaire-HAQ) were associated with HR-pQCT (Scanco Medical AG, Brüttisellen, Switzerland) parameters. Multiple linear regression models adjusted for clinical and laboratory variables, ROM and HAQ, were performed. RESULTS: Density, microarchitecture, and biomechanical parameters at the distal radius and tibia were significantly impaired in dSSc patients compared with healthy controls (p < 0.001). Multiple linear regression models showed that lower trabecular density (Tb.vBMD) (radius R2 = 0.561, p = 0.002; and tibia R2 = 0.533, p = 0.005), and lower trabecular number (Tb.N) (tibia R2 = 0.533, p = 0.005) were significantly associated with acroosteolysis. Higher trabecular separation (Tb.Sp) was associated with disease duration and higher HAQ-grip strength (radius R2 = 0.489, p = 0.013), while cortical density (Ct.vBMD) was associated with ROM (radius R2 = 0.294, p = 0.002). CONCLUSION: Bone microarchitecture in patients with dSSc, analyzed through HR-pQCT, showed impairment of trabecular and cortical bone at distal radius and tibia. Variables associated with hand involvement (acroosteolysis, quality of life-grip strength, and ROM) and disease duration may be considered prognostic factors of this bone impairment.

A tyrosine kinase-activating variant Asn666Ser in PDGFRB causes a progeria-like condition in the severe end of Penttinen syndrome.

Missense variants located to the "molecular brake" in the tyrosine kinase hinge region of platelet-derived growth factor receptor-ß, encoded by PFGFRB, can cause Penttinen-type (Val665Ala) and Penttinen-like (Asn666His) premature ageing syndromes, as well as infantile myofibromatosis (Asn666Lys and Pro660Thr). We have found the same de novo PDGFRB c.1997A>G p.(Asn666Ser) variants in two patients with lipodystrophy, acro-osteolysis and severely reduced vision due to corneal neovascularisation, reminiscent of a severe form of Penttinen syndrome with more pronounced connective tissue destruction. In line with this phenotype, patient skin fibroblasts were prone to apoptosis. Both in patient fibroblasts and stably transduced HeLa and HEK293 cells, autophosphorylation of PDGFRß was observed, as well as increased phosphorylation of downstream signalling proteins such as STAT1, PLCγ1, PTPN11/SHP2-Tyr580 and AKT. Phosphorylation of MAPK3 (ERK1) and PTPN11/SHP2-Tyr542 appeared unaffected. This suggests that this missense change not only weakens tyrosine kinase autoinhibition, but also influences substrate binding, as both PTPN11 tyrosines (Tyr542 and Tyr580) usually are phosphorylated upon PDGFR activation. Imatinib was a strong inhibitor of phosphorylation of all these targets, suggesting an option for precision medicine based treatment.

Expansion of the phenotype of Kosaki overgrowth syndrome.

Skeletal overgrowth is a characteristic of several genetic disorders that are linked to specific molecular signaling cascades. Recently, we established a novel overgrowth syndrome (Kosaki overgrowth syndrome, OMIM #616592) arising from a de novo mutation in PDGFRB, that is, c.1751C>G p.(Pro584Arg). Subsequently, other investigators provided in vitro molecular evidence that this specific mutation in the juxtamembrane domain of PDGFRB causes an overgrowth phenotype and is the first gain-of-function point mutation of PDGFRB to be reported in humans. Here, we report the identification of a mutation in PDGFRB, c.1696T>C p.(Trp566Arg), in two unrelated patients with skeletal overgrowth, further confirming the existence of PDGFRB-related overgrowth syndrome arising from mutations in the juxtamembrane domain of PDGFRB. A review of all four of these patients with an overgrowth phenotype and PDGFRB mutations revealed postnatal skeletal overgrowth, premature aging, cognitive impairment, neurodegeneration, and a prominent connective tissue component to this complex phenotype. From a functional standpoint, hypermorphic mutations in PDGFRB lead to Kosaki overgrowth syndrome, infantile myofibromatosis (OMIM #228550), and Penttinen syndrome (OMIM #601812), whereas hypomorphic mutations lead to idiopathic basal ganglia calcification (OMIM #615007). In conclusion, a specific class of mutations in PDGFRB causes a clinically recognizable syndromic form of skeletal overgrowth.

Acro-osteolysis and calcinosis in patient with scleroderma: A case report.

Acro-osteolysis is a rare disease characterized by bone resorption involving the distal phalanges of the hand. We present a unique case of progressive acro-osteolysis of the distal phalanges and articular calcifications in a patient with scleroderma. The calcified deposit in a proximal interphalangeal joint was excised under local anesthesia. The medical treatment was arranged under the supervision of a rheumatologist.

Altered chromatin organization and SUN2 localization in mandibuloacral dysplasia are rescued by drug treatment.

Mandibuloacral dysplasia type A (MADA) is a rare laminopathy characterized by growth retardation, craniofacial anomalies, bone resorption at specific sites including clavicles, phalanges and mandibula, mottled cutaneous pigmentation, skin rigidity, partial lipodystrophy, and insulin resistance. The disorder is caused by recessive mutations of the LMNA gene encoding for A-type lamins. The molecular feature of MADA consists in the accumulation of the unprocessed lamin A precursor, which is detected at the nuclear rim and in intranuclear aggregates. Here, we report the characterization of prelamin A post-translational modifications in MADA cells that induce alterations in the chromatin arrangement and dislocation of nuclear envelope-associated proteins involved in correct nucleo-cytoskeleton relationships. We show that protein post-translational modifications change depending on the passage number, suggesting the onset of a feedback mechanism. Moreover, we show that treatment of MADA cells with the farnesyltransferase inhibitors is effective in the recovery of the chromatin phenotype, altered in MADA, provided that the cells are at low passage number, while at high passage number, the treatment results ineffective. Moreover, the distribution of the lamin A interaction partner SUN2, a constituent of the nuclear envelope, is altered by MADA mutations, as argued by the formation of a highly disorganized lattice. Treatment with statins partially rescues proper SUN2 organization, indicating that its alteration is caused by farnesylated prelamin A accumulation. Given the major role of SUN1 and SUN2 in the nucleo-cytoskeleton interactions and in regulation of nuclear positioning in differentiating cells, we hypothesise that mechanisms regulating nuclear membrane-centrosome interplay and nuclear movement may be affected in MADA fibroblasts.

Type B mandibuloacral dysplasia with congenital myopathy due to homozygous ZMPSTE24 missense mutation.

Mutation in ZMPSTE24 gene, encoding a major metalloprotease, leads to defective prelamin A processing and causes type B mandibuloacral dysplasia, as well as the lethal neonatal restrictive dermopathy syndrome. Phenotype severity is correlated with the residual enzyme activity of ZMPSTE24 and accumulation of prelamin A. We had previously demonstrated that a complete loss of function in ZMPSTE24 was lethal in the neonatal period, whereas compound heterozygous mutations including one PTC and one missense mutation were associated with type B mandibuloacral dysplasia. In this study, we report a 30-year longitudinal clinical survey of a patient harboring a novel severe and complex phenotype, combining an early-onset progeroid syndrome and a congenital myopathy with fiber-type disproportion. A unique homozygous missense ZMPSTE24 mutation (c.281T>C, p.Leu94Pro) was identified and predicted to produce two possible ZMPSTE24 conformations, leading to a partial loss of function. Western blot analysis revealed a major reduction of ZMPSTE24, together with the presence of unprocessed prelamin A and decreased levels of lamin A, in the patient's primary skin fibroblasts. These cells exhibited significant reductions in lifespan associated with major abnormalities of the nuclear shape and structure. This is the first report of MAD presenting with confirmed myopathic abnormalities associated with ZMPSTE24 defects, extending the clinical spectrum of ZMPSTE24 gene mutations. Moreover, our results suggest that defective prelamin A processing affects muscle regeneration and development, thus providing new insights into the disease mechanism of prelamin A-defective associated syndromes in general.

[Acroosteolysis in PVC autoclave cleaners: history of an occupational disease]. / Nascita, sviluppo e scomparsa di una malattia professionale: la acroosteolisi dei pulitori manuali di autoclavi nella produzione di PVC.

OBJECTIVES: This paper examines the history of an occupational disease which has now disappeared: acroosteolysis of manual tank cleaners in the production of polyvinyl chloride (PVC), which is a rare disease characterized by destructive alterations of the distal phalanges of the hands. METHODS: All the available literature on this disease was examined. The history of acroosteolysis was studied within the general framework of the history of the discovery of adverse health effects of exposure to vinyl chloride, and this history was studied up to the end of the 1960's. RESULTS: The disease was observed for the first time in mid-1963 in Belgium (Jemeppe) in a chemical plant operated by Solvay, and affected two workers whose job was the manual cleaning of vessels used for the polymerization of vinyl chloride; similar cases occurred in almost all PVC production plants all over the world, but not in the plants where the main activity was the production of vinyl chloride monomer (VCM). Little more than one hundred cases are described in the scientific literature, and this number increases by a few dozen if we consider known but unpublished cases. These figures confirm the rarity of the disease, which peaked at the end of the 1960's and disappeared during the 1970's, probably due to the complete elimination of manual reactor cleaning. Observation of the disease lasted no more than fifteen years and the disease was not replicated in experimental conditions on animals. DISCUSSION: The disease was clinically characterized, had a short latency (from several months to several years), was rare and unequivocally linked to the manual cleaning of PVC polymerization tanks. However many questions still remain open: the period when the disease first appeared (many years after the start of PVC production in the world), the etiology of the disease (the most accredited hypothesis considers three concomitant factors: a chemical factor--one of the many substances used during polymerization, and particularly vinyl chloride monomer, a physical factor--microtraumas of the fingers during manual cleaning, individual susceptibility), the pathogenetic mechanism (in particular: the role of skin, respiratory, or digestive system, as entrance door), a method (or test) to screen subjects potentially predisposed to the disease. In our view acroosteolysis of manual tank cleaners in PVC production is an occupational disease which is distinct from "vinyl chloride disease" as identified by Viola (1974).

Faun tail naevus: a cutaneous marker of spinal dysraphism.

We describe three cases (one male and two females) of faun tail nevi, which is one of the most important cutaneous marker of spinal dysraphism. One of the patients presented with acro-osteolysis leading to auto amputation of the toes of the left foot, which required operative intervention. This lays stress on the early recognition of lumbar paraspinal skin lesions and early treatment to avoid irreversible sequelae.