Murine fibroblast growth factor receptor 1alpha isoforms mediate node regression and are essential for posterior mesoderm development.
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Alternative splicing in the fibroblast growth factor receptor 1 (Fgfr1) locus generates a variety of splicing isoforms, including FGFR1alpha isoforms, which contain three immunoglobulin-like loops in the extracellular domain of the receptor. It has been previously shown that embryos carrying targeted disruptions of all major isoforms die during gastrulation, displaying severe growth retardation and defective mesodermal structures. Here we selectively disrupted the FGFR1alpha isoforms and found that they play an essential role in posterior mesoderm formation during gastrulation. We show that the mutant embryos lack caudal somites, develop spina bifida, and die at 9.5-12.5 days of embryonic development because they are unable to establish embryonic circulation. The primary defect is a failure of axial mesoderm cell migration toward the posterior portions of the embryos during gastrulation, as revealed by regional marker analysis and DiI labeling. In contrast, the anterior migration of the notochord is unaffected and the embryonic structures rostral to the forelimb are relatively normal. These data demonstrate that FGF/FGFR1alpha signals are posteriorizing factors that control node regression and posterior embryonic development. (+info)
Segmental spinal dysgenesis: neuroradiologic findings with clinical and embryologic correlation.
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BACKGROUND AND PURPOSE: Segmental spinal dysgenesis (SSD) is a rare congenital abnormality in which a segment of the spine and spinal cord fails to develop properly. Our goal was to investigate the neuroradiologic features of this condition in order to correlate our findings with the degree of residual spinal cord function, and to provide insight into the embryologic origin of this disorder. We also aimed to clarify the relationship between SSD and other entities, such as multiple vertebral segmentation defects, congenital vertebral displacement, and caudal regression syndrome (CRS). METHODS: The records of patients treated at our institutions for congenital spinal anomalies were reviewed, and 10 cases were found to satisfy the inclusion criteria for SSD. Plain radiographs were available for review in all cases. MR imaging was performed in eight patients, one of whom also underwent conventional myelography. Two other patients underwent only conventional myelography. RESULTS: Segmental vertebral anomalies involved the thoracolumbar, lumbar, or lumbosacral spine. The spinal cord at the level of the abnormality was thinned or even indiscernible, and a bulky, low-lying cord segment was present caudad to the focal abnormality in most cases. Closed spinal dysraphisms were associated in five cases, and partial sacrococcygeal agenesis in three. Renal anomalies were detected in four cases, and dextrocardia in one; all patients had a neurogenic bladder. CONCLUSION: SSD is an autonomous entity with characteristic clinical and neuroradiologic features; however, SSD and CRS probably represent two faces of a single spectrum of segmental malformations of the spine and spinal cord. The neuroradiologic picture depends on the severity of the malformation and on its segmental level along the longitudinal embryonic axis. The severity of the morphologic derangement correlates with residual spinal cord function and with severity of the clinical deficit. (+info)
Transgenic rescue of congenital heart disease and spina bifida in Splotch mice.
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Pax3-deficient Splotch mice display neural tube defects and an array of neural crest related abnormalities including defects in the cardiac outflow tract, dorsal root ganglia and pigmentation. Pax3 is expressed in neural crest cells that emerge from the dorsal neural tube. Pax3 is also expressed in the somites, through which neural crest cells migrate, where it is required for hypaxial muscle development. Homozygous mutant Splotch embryos die by embryonic day 14. We have utilized the proximal 1.6 kb Pax3 promoter and upstream regulatory elements to engineer transgenic mice reproducing endogenous Pax3 expression in neural tube and neural crest, but not the somite. Over expression of Pax3 in these tissues reveals no discernible phenotype. Breeding of transgenic mice onto a Splotch background demonstrates that neural tube and neural crest expression of Pax3 is sufficient to rescue neural tube closure, cardiac development and other neural crest related defects. Transgenic Splotch mice survive until birth at which time they succumb to respiratory failure secondary to absence of a muscular diaphragm. Limb muscles are also absent. These results indicate that regulatory elements sufficient for functional expression of Pax3 required for cardiac development and neural tube closure are contained within the region 1.6 kb upstream of the Pax3 transcriptional start site. In addition, the single Pax3 isoform used for this transgene is sufficient to execute these developmental processes. Although the extracellular matrix and the environment of the somites through which neural crest migrates is known to influence neural crest behavior, our results indicate that Pax3-deficient somites are capable of supporting proper neural crest migration and function suggesting a cell autonomous role for Pax3 in neural crest. (+info)
Notochord-dependent expression of MFH1 and PAX1 cooperates to maintain the proliferation of sclerotome cells during the vertebral column development.
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During axial skeleton development, the notochord is essential for the induction of the sclerotome and for the subsequent differentiation of cartilage forming the vertebral bodies and intervertebral discs. These functions are mainly mediated by the diffusible signaling molecule Sonic hedgehog. The products of the paired-box-containing Pax1 and the mesenchyme forkhead-1 (Mfh1) genes are expressed in the developing sclerotome and are essential for the normal development of the vertebral column. Here, we demonstrate that Mfh1 like Pax1 expression is dependent on Sonic hedgehog signals from the notochord, and Mfh1 and Pax1 act synergistically to generate the vertebral column. In Mfh1/Pax1 double mutants, dorsomedial structures of the vertebrae are missing, resulting in extreme spina bifida accompanied by subcutaneous myelomeningocoele, and the vertebral bodies and intervertebral discs are missing. The morphological defects in Mfh1/Pax1 double mutants strongly correlate with the reduction of the mitotic rate of sclerotome cells. Thus, both the Mfh1 and the Pax1 gene products cooperate to mediate Sonic hedgehog-dependent proliferation of sclerotome cells. (+info)
Link between the CSF shunt and achievement in adults with spina bifida.
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OBJECTIVES: A few enterprising adults with shunt treated spina bifida live independently in the community, have a job in competitive employment, and drive to work in their own car. By contrast others with similar disability but lacking their motivation remain dependent on care and supervision. The aim of this study was to identify events in the history of their shunt which may have influenced their subsequent achievement. METHODS: Between June 1963 and January 1971 117 babies born in East Anglia with open spina bifida had their backs closed regardless of the severity of their condition. When reviewed in 1997 every case was ascertained. Sixty had died and the 57 survivors had a mean age of 30. These were assigned to two groups: achievers and non-achievers, according to their attainments in independence, employment, and use of a car. RESULTS: Of the 57 survivors nine had no shunt and eight of these were achievers. All were of normal intelligence (IQ>/=80) and only one was severely disabled. Of the 48 with shunts only 20 were achievers (OR 11.2, 95% confidence interval (95% CI) 1.3-96.8). Lack of achievement in these 48 was associated with revisions of the shunt, particularly when revisions were performed after the age of 2. Sixteen patients had never required a revision and 11 (69%) were achievers; 10 had had revisions only during infancy and five (50%) were achievers; 22 had had revisions after their second birthday and only four (18%) were achievers (p<0.001). Elective revisions were not performed in this cohort and in 75% of patients revisions had been preceded by clear symptoms of raised intracranial pressure. CONCLUSION: Revisions of the shunt, particularly after the age of 2, are associated with poor long term achievement in adults with spina bifida. (+info)
Spinal dysraphism in a newborn Holstein-Friesian calf.
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Spinal dysraphism, not associated with vertebral defect or arthrogryposis, was found in a 3-day-old Holstein-Friesian calf that was clinically diagnosed as having encephalopathy. The dysraphic lesion occurred in the sixth (C6) and seventh (C7) segments of the cervical spinal cord. Microscopically, the lesion was characterized by hydromyelia, syringomyelia, anomaly of the ventral median fissure, abnormal running of the myelinated nerve fibers in the white column, and absence of the central canal due to a developmental defect of the ependymal cells. (+info)
Condition severity and psychosocial functioning in pre-adolescents with spina bifida: disentangling proximal functional status and distal adjustment outcomes.
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OBJECTIVE: To examine relations between condition severity and psychosocial functioning in 70 8- and 9-year-old pre-adolescents with spina bifida by testing several direct, indirect, and mediated effects models for proximal functional status and distal adjustment outcomes. METHODS: Proximal functional status outcomes (e.g., degree of involvement in activities, scholastic competence, athletic competence, attentional problems) and distal adjustment outcomes (e.g., behavior problems, social competence) were assessed with mother, father, and teacher report. Severity variables included spinal lesion level, spina bifida classification, shunt status, ambulation status, number of shunt surgeries, and two severity composites. RESULTS: Condition severity was associated with the proximal functional status outcomes across parent and teacher report. In contrast, no significant relationships were found between the severity parameters and distal adjustment outcomes. Findings supported a proximal effects model of condition severity as well as an indirect effects model (e.g., presence of a shunt-->less scholastic competence-->less social competence) and were consistent with recent theoretical formulations (e.g., Wallander & Varni, 1995). CONCLUSIONS: Disentangling proximal functional status outcomes and distal adjustment outcomes is critical in studies of condition severity and psychosocial functioning. We discuss clinical implications. (+info)
East Ireland 1980-1994: epidemiology of neural tube defects.
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STUDY OBJECTIVE: The objective of the study was to describe the epidemiology of neural tube defects (NTD) in the eastern region of Ireland using the EUROCAT register of congenital malformations. DESIGN, SETTING AND PATIENTS: EUROCAT registries monitor the prevalence of congenital anomalies in defined populations using multiple sources for case ascertainment. All cases of NTD on the Dublin EUROCAT register born between 1980 and 1994 were extracted and analysed. The crude birth prevalence rate for all NTD, spina bifida, anencephaly and encephalocoele were calculated for each year. Parameters measured were: sex ratio, stillbirth rate, proportion of low birth-weight babies (< 2500 g) and the proportion who were premature (< 37 weeks gestation). MAIN RESULTS: Of 821 NTD cases, 419 (51.0%) had spina bifida, 322 (39.2%) had anencephaly, 69 (8.4%) had encephalocoele and 11 (1.3%) were iniencephalic. The crude birth prevalence of NTD decreased fourfold from 46.9/10,000 births in 1980 to 11.6/10,000 in 1994. The downward trend ceased during the early 1990's. Younger mothers had significantly higher rates of NTD affected births. Twenty two per cent of NTD cases had additional non-central nervous system anomalies. In 40 cases, there was a previous family history of NTD in siblings. Seasonal effects in birth prevalence were observed. Birth notification was the most frequent mechanism of ascertainment. CONCLUSION: There was a marked fall in the birth prevalence of NTD during the 15 year period. This change was real and not accounted for by pre-natal screening and diagnostic practises with termination of pregnancy, which is not legally permissible in Ireland. Dietary factors may have had an influence. Rates of NTD in this region are still higher than many other parts of Europe. Primary prevention strategies through increased folic acid intake are necessary to further reduce NTD affected births. (+info)