Hydrocephalus and arthrogryposis in an immunocompetent mouse model of ZIKA teratogeny: A developmental study

The teratogenic mechanisms triggered by ZIKV are still obscure due to the lack of a suitable animal model. Here we present a mouse model of developmental disruption induced by ZIKV hematogenic infection. The model utilizes immunocompetent animals from wild-type FVB/NJ and C57BL/6J strains, providing a better analogy to the human condition than approaches involving immunodeficient, genetically modified animals, or direct ZIKV injection into the brain. When injected via the jugular vein into the blood of pregnant females harboring conceptuses from early gastrulation to organogenesis stages, akin to the human second and fifth week of pregnancy, ZIKV infects maternal tissues, placentas and embryos/fetuses. Early exposure to ZIKV at developmental day 5 (second week in humans) produced complex manifestations of anterior and posterior dysraphia and hydrocephalus, as well as severe malformations and delayed development in 10.5 days post-coitum (dpc) embryos. Exposure to the virus at 7.5-9.5 dpc induces intra-amniotic hemorrhage, widespread edema, and vascular rarefaction, often prominent in the cephalic region. At these stages, most affected embryos/fetuses displayed gross malformations and/or intrauterine growth restriction (IUGR), rather than isolated microcephaly. Disrupted conceptuses failed to achieve normal developmental landmarks and died in utero. Importantly, this is the only model so far to display dysraphia and hydrocephalus, the harbinger of microcephaly in humans, as well as arthrogryposis, a set of abnormal joint postures observed in the human setting. Late exposure to ZIKV at 12.5 dpc failed to produce noticeable malformations. We have thus characterized a developmental window of opportunity for ZIKV-induced teratogenesis encompassing early gastrulation, neurulation and early organogenesis stages. This should not, however, be interpreted as evidence for any safe developmental windows for ZIKV exposure. Late developmental abnormalities correlated with damage to the placenta, particularly to the labyrinthine layer, suggesting that circulatory changes are integral to the altered phenotypes.

Molecular prenatal diagnosis for hereditary distal arthrogryposis type 2B

Autosomal dominant distal arthrogryposes (DAs) are a group of muscle diseases characterized by congenital contractures of the limbs. Currently, prenatal diagnosis of DAs depends upon ultrasound examination during late gestation. Recently, five genes encoding fast switch proteins located at 9p13.2, 11p15.5 and 17q13.1 were identified. These included TPM2, TNNI2/TNNT3, and MYH3/MYH8. Last year, we discovered a novel heterozygous mutation c.523_525delAAG (p.K175del) in the TNNI2 gene, which encodes the isoform of troponinI, in a seven-generation Chinese family affected with distal arthrogryposis type 2B (DA2B). Here, we report the molecular prenatal diagnosis of 3 high-risk fetuses of two women in the family by two-point linkage inferential analysis and deletion detection of the TNNI2 gene with chorionic villus sampling (CVS) or amniocentesis. To our knowledge, this is the first description of molecular prenatal diagnosis for DAs.

Escobar syndrome is a prenatal myasthenia caused by disruption of the acetylcholine receptor fetal gamma subunit

Escobar syndrome is a form of arthrogryposis multiplex congenita and features joint contractures, pterygia, and respiratory distress. Similar findings occur in newborns exposed to nicotinergic acetylcholine receptor (AChR) antibodies from myasthenic mothers. We performed linkage studies in families with Escobar syndrome and identified eight mutations within the gamma -subunit gene (CHRNG) of the AChR. Our functional studies show that gamma -subunit mutations prevent the correct localization of the fetal AChR in human embryonic kidney-cell membranes and that the expression pattern in prenatal mice corresponds to the human clinical phenotype. AChRs have five subunits. Two alpha, one beta, and one delta subunit are always present. By switching gamma to epsilon subunits in late fetal development, fetal AChRs are gradually replaced by adult AChRs. Fetal and adult AChRs are essential for neuromuscular signal transduction. In addition, the fetal AChRs seem to be the guide for the primary encounter of axon and muscle. Because of this important function in organogenesis, human mutations in the gamma subunit were thought to be lethal, as they are in gamma -knockout mice. In contrast, many mutations in other subunits have been found to be viable but cause postnatally persisting or beginning myasthenic syndromes. We conclude that Escobar syndrome is an inherited fetal myasthenic disease that also affects neuromuscular organogenesis. Because gamma expression is restricted to early development, patients have no myasthenic symptoms later in life. This is the major difference from mutations in the other AChR subunits and the striking parallel to the symptoms found in neonates with arthrogryposis when maternal AChR auto-antibodies crossed the placenta and caused the transient inactivation of the AChR pathway.

Prenatal diagnosis of Bruck syndrome

Bruck syndrome is an autosomal recessive connective tissue disorder combining features of osteogenesis imperfecta and arthrogryposis multiplex congenita. There are only few reports describing this rare syndrome of multiple fractures and joint contractures that is thought to be a subtype of osteogenesis imperfecta. We report the first case of prenatal diagnosis of this syndrome in a fetus at 23 weeks of gestation. Ultrasound findings included brachycephaly, retrognathia marked shortening and bowing of both femurs, bilateral fixed flexion of the elbows, bilateral fixed extension of the wrists and partially fixed flexion of the knees. The parents opted for termination of pregnancy. Macroscopic and radiologic examination of the aborted fetus confirmed the prenatal diagnosis, whereas morphological studies of the bone tissue found no hard evidence of osteogenesis imperfecta, probably due to the early stage of pregnancy and the heterogeneity of the syndrome itself.

Plasma from human mothers of fetuses with severe arthrogryposis multiplex congenita causes deformities in mice

Arthrogryposis multiplex congenita (AMC) is characterized by fixed joint contractures and other deformities, sometimes resulting in fetal death. The cause is unknown in most cases, but some women with fetuses affected by severe AMC have serum antibodies that inhibit fetal acetylcholine receptor (AChR) function, and antibodies to fetal antigens might play a pathogenic role in other congenital disorders. To investigate this possibility, we have established a model by injecting pregnant mice with plasma from four anti-AChR antibody-positive women whose fetuses had severe AMC. We found that human antibodies can be transferred efficiently to the mouse fetus during the last few days of fetal life. Many of the fetuses of dams injected with AMC maternal plasmas or Ig were stillborn and showed fixed joints and other deformities. Moreover, similar changes were found in mice after injection of a serum from one anti-AChR antibody-negative mother who had had four AMC fetuses. Thus, we have confirmed the role of maternal antibodies in cases of AMC associated with maternal anti-AChR, and we have demonstrated the existence of pathogenic maternal factors in one other case. Importantly, this approach can be used to look at the effects of other maternal human antibodies on development of the fetus.

Ovine fetal malformations induced by in utero inoculation with Main Drain, San Angelo, and LaCrosse viruses

The teratogenic potential of three bunyaviruses, two California serogroup bunyaviruses, LaCrosse virus and San Angelo virus, and a Bunyamwera serogroup member, Main Drain virus, in sheep was studied following in utero inoculation of ewes in early gestation. Although Main Drain virus appeared to be most teratogenic, all three viruses induced a range of lesions including arthrogryposis, hydrocephalus, fetal death, axial skeletal deviations, anasarca, and oligohydramnios. The teratogenic effects of these viruses are identical to those described in ovine infections by Cache Valley and Akabane viruses. Demonstration of a common bunyaviral tropism for fetal tissue infection that results in congenital brain and musculoskeletal malformations provides evidence that human in utero infection by bunyaviruses could result in similar malformations in human infants.

Neurogenic arthrogryposis multiplex congenita: clinical and MRI findings

A clinical and magnetic resonance imaging (MRI) study on a selected group of 11 children, with a diagnosis of neurogenic arthrogryposis multiplex congenita (AMC) based on clinical, electromyographic, and muscle biopsy findings, is presented to determine the extent of central nervous system involvement in AMC. Family history, pregnancy, perinatal problems, other abnormalities, and epileptic seizures were reviewed. Neurologic examination, electroencephalography, intellectual assessment, and MRI study both of spinal cord and brain were performed. The clinical and laboratory findings disclosed evidence of spinal cord lesions with involvement of anterior horn cell function in all patients, and impairment of cerebral function in 5 patients. MRI revealed spinal cord atrophy in 3 patients, diffuse atrophy in 2 patients, and involved thoraco-lumbar segments in 1 patient. Cranial MRI studies demonstrated features of developmental brain abnormalities in 3 patients, cortical frontal atrophy in 2, and was normal in 4. In neurogenic AMC patients, MRI examination of the spinal cord and brain may help to clarify the pathogenesis of the disease and is helpful for prognostic and therapeutic purposes.

Further evidence that arthrogryposis multiplex congenita in the human sometimes is caused by an intrauterine vascular accident

A 7 1/2-year-old girl with arthrogryposis multiplex congenita of the amyoplasia type in association with intestinal atresias, gastroschisis, Möbius anomaly, and hypoplasia of the pectoral, biceps, and deltoid muscles is described. Several combinations of these birth defects have been previously described. There is considerable evidence that gastroschisis, intestinal atresia, Poland sequence, and Möbius anomaly each has a vascular pathogenesis. Based on the associations seen in this child and past reports of more limited, similar cooccurrences, we suggest that arthrogryposis multiplex congenita may sometimes be caused by an intrauterine vascular catastrophe.

The etiology of arthrogryposis (multiple congenital contracture)

In laboratory animals, prenatal contractures have been induced by viruses, neuromuscular blocking agents, toxins, insecticides, hyperthermia, and limb immobilization. In agricultural animals, prenatal contractures are related to pregnant animals foraging on plants containing toxic alkaloids. Epizootics of prenatal contractures in cattle have been related to Akabane viral infections, which can now be prevented by vaccination. Human arthrogryposis (multiple congenital contracture) may occur in any synovial joint in a large variety of combinations. Several lethal syndromes commonly associated with prenatal contractures (Pena Shokeir 1 and 11, Potter's) provide supportive evidence for the following concept of prenatal contracture etiology. Evidence is provided that indicates that the following multiple etiologic factors are related to production of human arthrogryposis: mutagenic agents, mitotic abnormalities, toxic chemicals or drugs, hyperthermia, neuromuscular blocking agents, and mechanical immobilization. These multiple factors mediate their effect via the central nervous system (craniospinal motor neuraxis), motor end-plates, or by primary degeneration of muscle. The resultant effect is loss of muscle mass with imbalance of muscle power at the joints, which provokes a collagenic response (Law of the Connective Tissue). The collagenic response consists of partial replacement of muscle volume and collagenous thickening of the joint capsules. The latter process leads to joint fixation.

Experimental study on the etiology of congenital multiple arthrogryposis

The effect of temporary immobility of the muscles in the embryo, induced by continuous infusion of d-tubocurarine into the ovum, was studied in 31 chick embryos. The ankle and foot joints showed flexion contractures with equal frequency, but the knees were less severely affected. Histological examination demonstrated peri-articular and intra-articular fibrosis, and fibrosis of the muscles of the limb. These experimental lesions closely resemble those of arthrogryposis. It is therefore suggested that the aetiology of human arthrogryposis may be based on a common pathogenetic mechanism; lack of joint movement during embryonic life.

The arthrogrypotic foot plan of management and results of treatment

Fifty-one arthrogrypotic feet have been treated and followed by the Pediatric Orthopaedic Unit, Tufts New England Medical Center, (1970-1980). Forty of the 51 feet presented as equinovarus with the residual divided among metatarsus adductus, vertical tali, and calcaneovalgus. Equinovarus deformities are the most resistant in all cases. Corrective casts are applied for at least the first 3 months of life. Surgical procedures were then initiated with any evidence of lack of progression of treatment. Varus and equinus were treated by an extensive posterior and medial release. Lateral soft tissue releases in addition to calcaneocuboid fusion or cuboid osteotomy were necessary in 24 of the 70 operations. Recurrence rate has been a problem in the simple type of posterior release including only an Achilles tendon lengthening, and posterior capsulotomy of the ankle and subtalar joint. Talectomy has been carried out in four feet and appears to be one type of reasonable salvage procedure in smaller children with recurrent varus. Treatment is difficult in these patients but a plantigrade foot should be achieved in all cases.

Whence the arthrogrypotics?

During the course of a nation-wide survey of patients with bone and joint deformities, twenty-six individuals with arthrogryposis multiplex congenita, in the narrow and precise sense of the term, were investigated. No patient was more than twenty-four years of age. However, on a basis of the figures of population, it can be estimated that 21-0 +/- 6-5 older affected individuals should have been encountered. Furthermore, there was a relative excess of younger children. The series was reasonably unbiased, and as arthrogryposis is non-lethal the deficiency of affected adults is an anomalous finding. It is tentatively suggested that arthrogryposis might result from the intra-uterine influence of an unknown environmental agent which has been present in South Africa for only a limited period of time. Detection of this factor could be an important step in the prevention of the disease.