Polytopic anomalies with agenesis of the lower vertebral column

Caudal Regression Syndrome-A Review Focusing on Genetic Associations

Caudal regression syndrome (CRS) represents a spectrum of clinical phenotypes with varying degrees of malformation of the lower body with involvement of structures deriving from all 3 layers of the trilaminar embryo. We review areas of active investigation in the diagnosis, etiology, epidemiology, and treatment of the disease with a focus on underlying genetics. CRS pathobiology is complex and multifactorial with a significant contribution from environmental factors as evidenced in twin studies. Contemporary genomic and genetic investigations in both human primary tissue and murine in vitro and in vivo models implicate various genes associated with caudal differentiation and neural cell migration in embryogenesis. A large number of identified targets center around the metabolic regulation of retinoic acid and its derivatives. Dysregulation of retinoic acid homeostasis has been associated with abnormal embryonic cell migration, differentiation, and organogenesis with resulting malformations and agenesis in both a laboratory and a clinical setting. There appears to be a significant overlap in potential genetic targets with CRS and other developmental syndromes with similar presentations, such as VACTERL (vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities) association. CRS represents a spectrum of caudal developmental abnormalities with treatment options limited to mild and moderate expressions of disease. Continued research is necessary to further clarify mechanisms of disease pathobiology and complex polygenetic and environmental interaction. Despite this, progress has been made in identifying genetic targets and downstream effectors contributing to preclinical and clinical progression.

Perosomus elumbis in a stillborn rhesus macaque (Macaca mulatta): A case report

Perosomus Elumbis (PE) is a rare congenital disorder characterized by absence of caudal spine (lumbar, sacral, and coccygeal vertebrae). Here, we present the first reported case of PE in a rhesus macaque (Macaca mulatta) and relate our findings to those described in other species.

Fetal cervical hyperextension in arthrogryposis

Perhaps the most dramatic position of a newborn after delivery is when there is hyperextension of the neck and spine. It will have been presented in utero and today, almost always, such babies will have been delivered by C-section. The associated anomalies are variable. The process(es) that can lead to cervical hyperextension is/are largely unknown. The outcome is variable from lethal to completely resolve. Individuals with arthrogryposis and in particular with Amyoplasia appear to have an increased frequency of neck, cervical, and spine hyperextension at birth. We present here 41 cases of arthrogryposis (mainly Amyoplasia) with fetal cervical hyperextension. The outlook is surprisingly good if spinal cord trauma does not occur. Ultrasound late in pregnancy when arthrogryposis is recognized prenatally should determine whether cervical hyperextension has developed, so that appropriate preventive measures can be taken.

A rare case of pelvic bone duplication

Iliac bone malformations are rare and result from early disturbance of the genetic and epigenetic processes that come together to form the pelvic girdle. We report the case of a 5-month-old boy found to have a duplication of the ilium and describe the likely causes of this very rare malformation.

Pediatric Spinal Ultrasound: Neonatal and Intraoperative Applications

The purpose of this article is to review the use of ultrasound as a screening tool for spinal diseases in neonates and infants and its intraoperative value in selected pediatric neurosurgical disorders. A review of spinal embryology followed by a description of common spinal diseases in neonates assessed with ultrasound is presented. Indications for spinal ultrasound in neonates, commonly identified conditions, and the importance of magnetic resonance imaging in selected cases are emphasized. Additionally, the use of ultrasound in selected neurosurgical spinal diseases in pediatric patients is presented with magnetic resonance imaging and intraoperative correlation. Technique, limitations, and pitfalls are discussed.

Lumbosacral agenesis in a cat

Case summary

Lumbosacral agenesis is a rare congenital condition reported in children. We report a 17-week-old female domestic shorthair cat with lumbosacral agenesis on whole-body radiographs. The cat was euthanized shortly thereafter presentation. A necropsy was not permitted.

Relevance and novel information

This is the first reported feline case of lumbosacral agenesis.

Novel Mode of Defective Neural Tube Closure in the Non-Obese Diabetic (NOD) Mouse Strain

Failure to close the neural tube results in birth defects, with severity ranging from spina bifida to lethal anencephaly. Few genetic risk factors for neural tube defects are known in humans, highlighting the critical role of environmental risk factors, such as maternal diabetes. Yet, it is not well understood how altered maternal metabolism interferes with embryonic development, and with neurulation in particular. We present evidence from two independent mouse models of diabetic pregnancy that identifies impaired migration of nascent mesodermal cells in the primitive streak as the morphogenetic basis underlying the pathogenesis of neural tube defects. We conclude that perturbed gastrulation not only explains the neurulation defects, but also provides a unifying etiology for the broad spectrum of congenital malformations in diabetic pregnancies.

A retrotransposon insertion in the 5' regulatory domain of Ptf1a results in ectopic gene expression and multiple congenital defects in Danforth's short tail mouse

Danforth's short tail mutant (Sd) mouse, first described in 1930, is a classic spontaneous mutant exhibiting defects of the axial skeleton, hindgut, and urogenital system. We used meiotic mapping in 1,497 segregants to localize the mutation to a 42.8-kb intergenic segment on chromosome 2. Resequencing of this region identified an 8.5-kb early retrotransposon (ETn) insertion within the highly conserved regulatory sequences upstream of Pancreas Specific Transcription Factor, 1a (Ptf1a). This mutation resulted in up to tenfold increased expression of Ptf1a as compared to wild-type embryos at E9.5 but no detectable changes in the expression levels of other neighboring genes. At E9.5, Sd mutants exhibit ectopic Ptf1a expression in embryonic progenitors of every organ that will manifest a developmental defect: the notochord, the hindgut, and the mesonephric ducts. Moreover, at E 8.5, Sd mutant mice exhibit ectopic Ptf1a expression in the lateral plate mesoderm, tail bud mesenchyme, and in the notochord, preceding the onset of visible defects such as notochord degeneration. The Sd heterozygote phenotype was not ameliorated by Ptf1a haploinsufficiency, further suggesting that the developmental defects result from ectopic expression of Ptf1a. These data identify disruption of the spatio-temporal pattern of Ptf1a expression as the unifying mechanism underlying the multiple congenital defects in Danforth's short tail mouse. This striking example of an enhancer mutation resulting in profound developmental defects suggests that disruption of conserved regulatory elements may also contribute to human malformation syndromes.

Birth defects are a major cause of childhood morbidity and mortality. We studied the Danforth's short tail mouse, a classic mouse model of birth defects involving the skeleton, gut, and urinary system. We precisely localized the mutation responsible for these birth defects to a 42.8-kb segment on chromosome 2 and identified the mutation as an 8.5-kb transposon that disrupts highly conserved regulatory sequences upstream of the Pancreas Specific Transcription Factor, 1a (Ptf1a). The insertion disrupts a Ptf1a regulatory domain that is highly conserved across evolution and results in spatiotemporal defects in Ptf1a expression: we detected increased expression, temporally premature expression, and (most important for elucidating the mutant phenotype) the ectopic expression of Ptf1a in the notochord, hindgut, and mesonephros—the three sites that will give rise to organ defects in Danforth's short tail mouse. Our data also provide a striking example of how a noncoding, regulatory mutation can produce transient spatio-temporal dsyregulation of gene expression and result in profound developmental defects, highlighting the critical role of noncoding elements for coordinated gene expression in the vertebrate genome. Finally, these data provide novel insight into the role of Ptf1a in embryogenesis and lay the groundwork for elucidation of novel mechanisms underlying birth defects in humans.

Association of DiGeorge anomaly and caudal dysplasia sequence in a neonate born to a diabetic mother

AIM/OBJECTIVE

Several studies have demonstrated a significantly increased risk of specific patterns of congenital anomalies in infants born to diabetic mothers. In particular, caudal dysplasia sequence has been linked to pregnancy complicated by maternal diabetes. In addition, several cases of infants born to diabetic mothers presenting with features of DiGeorge anomaly have been reported. Infants with DiGeorge anomaly can display additional manifestations within the spectrum of caudal dysplasia sequence, including vertebral anomalies and renal agenesis.

METHODS

We report a neonate presenting with the co-occurrence of features of both DiGeorge anomaly and caudal dysplasia sequence, born to a mother with poorly controlled insulin-dependent diabetes.

RESULTS

The patient was affected by truncus arteriosus type A1 and hypertrophic cardiomyopathy.

CONCLUSION

Maternal diabetes can cause a spectrum of manifestations, expressing with isolated DiGeorge anomaly or caudal dysplasia sequence, with intermediate phenotypes or with the co-occurrence of both the congenital anomalies in the same patient. The present observations argue for a feasible link between truncus arteriosus with hypertrophic cardiomyopathy, DiGeorge anomaly, and maternal diabetes.

Perosomus elumbis in a puppy

A 2-day-old poodle puppy was seen to have hypoplastic and arthrogrypotic hindlimbs and no tail. Palpation revealed an absence of lumbar and sacral vertebrae. At necropsy examination, the colon had a blind ending at the umbilical area, there were no urinary system organs, the spinal cord ended at the thoracic level and no genital system organs were found except for a structure similar to a rudimentary penis. The pelvis was abnormal with no articulation with the spine. This congenital anomaly was consistent with perosomus elumbis, a rare condition of unknown aetiology with few reported cases.

Caudal regression in adrenocortical dysplasia (acd) mice is caused by telomere dysfunction with subsequent p53-dependent apoptosis

Adrenocortical dysplasia (acd) is a spontaneous autosomal recessive mouse mutation that exhibits a pleiotropic phenotype with perinatal lethality. Mutant acd embryos have caudal truncation, vertebral segmentation defects, hydronephrosis, and limb hypoplasia, resembling humans with Caudal Regression syndrome. Acd encodes Tpp1, a component of the shelterin complex that maintains telomere integrity, and consequently acd mutant mice have telomere dysfunction and genomic instability. While the association between genomic instability and cancer is well documented, the association between genomic instability and birth defects is unexplored. To determine the relationship between telomere dysfunction and embryonic malformations, we investigated mechanisms leading to the caudal dysgenesis phenotype of acd mutant embryos. We report that the caudal truncation is caused primarily by apoptosis, not altered cell proliferation. We show that the apoptosis and consequent skeletal malformations in acd mutants are dependent upon the p53 pathway by genetic rescue of the limb hypoplasia and vertebral anomalies with p53 null mice. Furthermore, rescue of the acd phenotype by p53 deficiency is a dosage-sensitive process, as acd/acd, p53(-/-) double mutants exhibit preaxial polydactyly. These findings demonstrate that caudal dysgenesis in acd embryos is secondary to p53-dependent apoptosis. Importantly, this study reinforces a significant link between genomic instability and birth defects.

Caudal regression syndrome and popliteal webbing in connection with maternal diabetes mellitus: a case report and literature review

Introduction

Most cases of caudal regression are sporadic or associated with gestational/maternal diabetes. The condition is thought to be part of a spectrum including imperforate anus, sacral agenesis and sirenomelia. Infants of diabetic mothers have two to three times the average incidence of congenital anomalies.

Case Presentation

We report on a 7-year-old boy from non-consanguineous family in Austria was born with features of caudal regression syndrome. A constellation of malformation complex such as caudal regression syndrome and anorectal malformation complex were evident at birth. Of great interest was the abnormal articulation between the pelvis and the remaining abnormal spine. Spinal-pelvic instability, dislocation of the hip, and knee-flexion contracture associated with popliteal webbing were the major orthopaedic abnormalities.

Conclusion

We showed that an offspring of a diabetic mother was at significant risk of developing caudal regression syndrome. Our present patient demonstrated type1 of Welch and Aterman classification. There was total sacral agenesis associated with subtotal lumbar agenesis. The lowest vertebrae were resting above an iliac amphiathrosis. We strongly encourage primary care providers to discuss the consequences of maternal diabetes mellitus as part of routine anticipatory guidance for antenatal/prenatal management. Careful diabetic control in the preconceptional period and the first eight weeks of pregnancy may lower the chances of congenital anomalies.

Defective somitogenesis and abnormal vertebral segmentation in man

In recent years molecular genetics has revolutionized the study of somitogenesis in developmental biology and advances that have taken place in animal models have been applied successfully to human disease. Abnormal segmentation in man is a relatively common birth defect and advances in understanding have come through the study of cases clustered in families using DNA linkage analysis and candidate gene approaches, the latter stemming directly from knowledge gained through the study of animal models. Only a minority of abnormal segmentation phenotypes appear to follow Mendelian inheritance but three genes--DLL3, MESP2 and LNFG--have now been identified for spondylocostal dysostosis (SCD), a spinal malformation characterized by extensive hemivertebrae, trunkal shortening and abnormally aligned ribs with points of fusion. In affected families autosomal recessive inheritance is followed. These genes are all important components of the Notch signaling pathway. Other genes within the pathway cause diverse phenotypes such as Alagille syndrome (AGS) and CADASIL, conditions that may have their origin in defective vasculogenesis. This review deals mainly with SCD, with some consideration of AGS. Significant future challenges lie in identifying causes of the many abnormal segmentation phenotypes in man but it is hoped that combined approaches in collaboration with developmental biologists will reap rewards.

Caudal dysgenesis, sirenomelia, and situs inversus totalis: a primitive defect in blastogenesis

Caudal dysgenesis (CD) constitutes a heterogeneous spectrum of congenital caudal anomalies, including varying degrees of agenesis of the vertebral column, as well as anorectal and genitourinary anomalies. Sirenomelia, characterized by a fusion of the lower limbs, could represent the most severe end of this spectrum. The two main debated pathogenic hypotheses are an aberrant vascular supply versus a primary axial mesoderm defect. We present the autopsy findings of two fetuses of non-diabetic mothers, with normal karyotype. Both fetuses presented situs inversus associated with a CD, in one case consisting of sirenomelia, establishing a very rare association profile that might be random. This association also suggests the occurrence of a common pathogenic mechanism, in accordance to recent genetic data, such as displayed in the Kif3A murine mutation phenotype. Some cases of sirenomelia and CD could represent developmental field defects of blastogenesis involving the caudal mesoderm, rather than being related to vascular insufficiency.

Abnormal vertebral segmentation and the notch signaling pathway in man

Abnormal vertebral segmentation (AVS) in man is a relatively common congenital malformation but cannot be subjected to the scientific analysis that is applied in animal models. Nevertheless, some spectacular advances in the cell biology and molecular genetics of somitogenesis in animal models have proved to be directly relevant to human disease. Some advances in our understanding have come through DNA linkage analysis in families demonstrating a clustering of AVS cases, as well as adopting a candidate gene approach. Only rarely do AVS phenotypes follow clear Mendelian inheritance, but three genes-DLL3, MESP2, and LNFG-have now been identified for spondylocostal dysostosis (SCD). SCD is characterized by extensive hemivertebrae, trunkal shortening, and abnormally aligned ribs with points of fusion. In familial cases clearly following a Mendelian pattern, autosomal recessive inheritance is more common than autosomal dominant and the genes identified are functional within the Notch signaling pathway. Other genes within the pathway cause diverse phenotypes such as Alagille syndrome (AGS) and CADASIL, conditions that may have their origin in defective vasculogenesis. Here, we deal mainly with SCD and AGS, and present a new classification system for AVS phenotypes, for which, hitherto, the terminology has been inconsistent and confusing.

Congenital Anomalies of the Spine

The complexity of the congenital anomalies of the spine can make the neuroradiologic diagnosis challenging. Knowledge of spinal embryology greatly helps in the understanding and classification of these anomalies. We use the classification devised by Tortori-Donati and Rossi and find it helpful from clinical and imaging standpoints. We believe that most patients who have known or suspected congenital spinal anomalies benefit from MR imaging.

Reassessment of holoprosencephaly–diencephalic hamartoblastoma (HDH) association

We report on a 23-week fetus with a hypothalamic hamartoma, lobar holoprosencephaly, right anophthalmia, and facial asymmetry, features which are consistent with the holoprosencephaly-diencephalic hamartoblastoma (HDH) association. In an attempt to better delineate HDH, we reviewed 19 published patients with similar features. The HDH clinical spectrum ranges from classic holoprosencephaly with micro/anophthalmia, multiple additional findings in non-contiguous structures and early lethality, to isolated microforms of holoprosencephaly. Associated cephalic features mainly include cortical/neuronal migration defects (39%), meningeal anomalies (28%), brainstem/posterior fossa malformations (22%), dysmorphic ears (41%), facial asymmetry (35%), and hypoplastic mandible (29%). Fifty-three percent of patients have additional extra-cephalic malformations, for example, vertebral/rib segmentation defects (50%), hypo/aplastic lungs (38%), congenital heart defect (29%), and urinary anomalies (29%). HDH shows etiological heterogeneity, that is, teratogenic exposure, chromosome imbalances, autosomal recessive as well as dominant "de novo" mutations. Several features could directly result from a disruptive sequence caused by an early hamartoma which alters the development of forebrain, hindbrain, meninges, and 1st-2nd branchial arches, although the pleiotropic action of genetic/environmental factors cannot be excluded. HDH does not emerge as a distinct syndrome, but other hypotheses, including separate conditions within a common pathway and the developmental field defect theory, are discussed.

Segmentation anomalies of vertebrae and ribs with other abnormalities of blastogenesis: syndromes or associations?

On the basis of two recently studied human fetuses and the historical records and remnant 19th century skeletons in the Museum Vrolik in Amsterdam, we have begun an analysis of an unusual form of somite dysgenesis. This disorder includes vertebral and costal segmentation defects with or without (distal) limb malformation and deformities, anogenital anomalies, unusual colonic atresia, abdominal wall and diaphragmatic defect, Central nervous system abnormality with large head, and severe neurohypotrophic lower limb deformities. This study suggests the existence of an axial vertebral/costal dysgenesis complex with apparently or nearly normal number of cervical vertebrae. There also is some overlap with lumbosacral agenesis but different from the autosomal recessive entities Jarcho-Levin syndrome or spondylocostal dysostosis. To date, no associated heart defects have been noted.

Implication of Wt1 in the pathogenesis of nephrogenic failure in a mouse model of retinoic acid-induced caudal regression syndrome

Renal malformations are common human birth defects that sometimes occur in the context of the caudal regression syndrome. Here, we found that exposure of pregnant mice to all-trans retinoic acid, at a time when the metanephros has yet to form, causes a failure of kidney development along with caudal regression. Maternal treatment with Am580 (retinoic acid receptor alpha agonist) also induced similar patterns of kidney maldevelopment in the fetus. In metanephroi from retinoic acid-treated pregnancies, renal mesenchyme condensed around the ureteric bud but then failed to differentiate into nephrons, instead undergoing involution by fulminant apoptosis to produce a renal agenesis phenotype. Results of whole organ cultures in serum-free medium, and also tissue recombination experiments, showed that the nephrogenic defect was intrinsic to the kidney and that it resided in the metanephric mesenchyme and not the ureteric bud. Renal mesenchyme from control embryos expressed Wilms' tumor 1 (Wt1), but this transcription factor, which is indispensable for kidney development, failed to express in metanephroi of retinoic acid-exposed embryos. Wt1 expression and organogenesis were both restored, however, when metanephroi from retinoic acid-treated pregnancies were grown in serum-containing media. Our data illuminate the pathobiology of a severe, teratogen-induced kidney malformation.

A dual fate of the hindlimb muscle mass: cloacal/perineal musculature develops from leg muscle cells

The cloaca serves as a common opening to the urinary and digestive systems. In most mammals, the cloaca is present only during embryogenesis, after which it undergoes a series of septation events leading to the formation of the anal canal and parts of the urogenital tract. During embryogenesis it is surrounded by skeletal muscle. The origin and the mechanisms regulating the development of these muscles have never been determined. Here, we show that the cloacal muscles of the chick originate from somites 30-34, which overlap the domain that gives rise to leg muscles (somites 26-33). Using molecular and cell labelling protocols, we have determined the aetiology of cloacal muscles. Surprisingly, we found that chick cloacal myoblasts first migrate into the developing leg bud and then extend out of the ventral muscle mass towards the cloacal tubercle. The development of homologous cloacal/perineal muscles was also examined in the mouse. Concordant with the results in birds, we found that perineal muscles in mammals also develop from the ventral muscle mass of the hindlimb. We provide genetic evidence that the perineal muscles are migratory, like limb muscles, by showing that they are absent in metd/d mutants. Using experimental embryological procedures (in chick) and genetic models (in chick and mouse), we show that the development of the cloacal musculature is dependent on proximal leg field formation. Thus, we have discovered a novel developmental mechanism in vertebrates whereby muscle cells first migrate from axially located somites to the pelvic limb, then extend towards the midline and only then differentiate into the single cloacal/perineal muscles.

Diaphanospondylodysostosis (DSD): Confirmation of a recessive disorder with abnormal vertebral ossification and nephroblastomatosis

We report on four patients from three families, with similar radiological findings: absent (or severely delayed) ossification of vertebral bodies and associated anomalies. The babies were stillborn or died soon after birth of respiratory insufficiency. Two patients are sibs (female and male) born to first cousin Malian parents. The two others were non-consanguineous. This perinatally lethal entity comprises short neck, short wide thorax, and normally shaped limbs. Associated, inconstant anomalies are myelomeningocele, cystic kidneys with nephrogenic rests (in the sibs), and cleft palate. Radiologically, the hallmarks are absence of ossification of the vertebral bodies and sacrum, abnormal position of the vertebral pedicles, which are lamellar and angulated, ribbon-like ribs reduced in number, narrow pelvis, upward widening of the iliac wings, and unusual tilt of the ischiopubic rami, contrasting with the normal appendicular skeleton. Maroteaux briefly described one of the patients in the 2002 edition of "Maladies osseuses de l'enfant" and three sibs with similar renal and radiological findings were reported in 2003 in this Journal. Combined with the latter cases, these four new patients allow delineation of a specific lethal AR syndrome with ossification defect of the axial skeleton and renal dysplasia. We propose to name this entity diaphanospondylodysostosis.

Urogenital and caudal dysgenesis in adrenocortical dysplasia (acd) mice is caused by a splicing mutation in a novel telomeric regulator

Adrenocortical dysplasia (acd) is a spontaneous autosomal recessive mouse mutant with developmental defects in organs derived from the urogenital ridge. In surviving adult mutants, adrenocortical dysplasia and hypofunction are predominant features. Adults are infertile due to lack of mature germ cells, and 50% develop hydronephrosis due to ureteral hyperplasia. We report the identification of a splice donor mutation in a novel gene, which is the mouse ortholog of a newly discovered telomeric regulator. This gene (Acd) has recently been characterized as a novel component of the TRF1 protein complex that controls telomere elongation by telomerase. Characterization of Acd transcripts in mutant animals reveals two abnormal transcripts, consistent with a splicing defect. Expression of a wild-type Acd transgene in acd mutants rescues the observed phenotype. Most mutants die within 1-2 days of life on the original genetic background. Analysis of these mutant embryos reveals variable, yet striking defects in caudal specification, limb patterning and axial skeleton formation. In the tail bud, reduced expression of Wnt3a and Dll1 correlates with phenotypic severity of caudal regression. In the limbs, expression of Fgf8 is expanded in the dorsal-ventral axis of the apical ectodermal ridge and shortened in the anterior-posterior axis, consistent with the observed loss of anterior digits in older embryos. The axial skeleton of mutant embryos shows abnormal vertebral fusions in cervical, lumbar and caudal regions. This is the first report to show that a telomeric regulator is required for proper urogenital ridge differentiation, axial skeleton specification and limb patterning in mice.

Overlap between VACTERL and hemifacial microsomia illustrating a spectrum of malformations seen in axial mesodermal dysplasia complex (AMDC)

We describe a male infant born to consanguineous healthy parents with multiple congenital anomalies of the skeleton and internal organs. His phenotype displays an overlap between VACTERL and hemifacial microsomia (oculo-auriculo-vertebral spectrum/OAV). In addition, striking asymmetry of the malformations further supports the classification as part of the "axial mesodermal dysplasia complex" (AMDC) which is supposed to arise from disturbed mesodermal cell migration during early blastogenesis. The present case was instructive to review the continuous spectrum of AMDC related anomalies.

A newly recognized autosomal recessive syndrome with abnormal vertebral ossification, rib abnormalities, and nephrogenic rests

We describe three cases of a severe malformation syndrome in siblings of both sexes. The characteristic features observed were absent intrauterine ossification of an apparently normal cartilaginous spinal column; rib abnormalities, with unossified segments and posterior gaps; thoracic hypoplasia; and multiple intralobar nephrogenic rests in the kidneys. This syndrome can be identified in early pregnancy by ultrasound scans due to the lack of ossification of the thoraco-lumbar spine and its association with increased nuchal translucency thickness. We suggest that this is a newly recognized autosomal recessive syndrome.

Caudal dysgenesis in Islet-1 transgenic mice

Maternal diabetes during pregnancy is responsible for the occurrence of diabetic embryopathy, a spectrum of birth defects that includes heart abnormalities, neural tube defects, and caudal dysgenesis syndromes. Here, we report that mice transgenic for the homeodomain transcription factor Isl-1 develop profound caudal growth defects that resemble human sacral/caudal agenesis. Isl-1 is normally expressed in the pancreas and is required for pancreas development and endocrine cell differentiation. Aberrant regulation of this pancreatic transcription factor causes increased mesodermal cell death, and the severity of defects is dependent on transgene dosage. Together with the finding that mutation of the pancreatic transcription factor HLXB9 causes sacral agenesis, our results implicate pancreatic transcription factors in the pathogenesis of birth defects associated with diabetes.

Defects of blastogenesis

Ever more frequent and closer involvement by clinical geneticists and counselors in the prenatal assessment of development mandates a better understanding of all stages of human ontogeny, but especially those of earliest development during which most of the lethal and all of the gross, multiple and complex defects of morphogenesis arise. Because of the phenomenon of universality, i.e., identical molecular inductive mechanisms involved in the process of embryonic pattern formation in all vertebrates, experimental animals indeed are a most valuable approach to an understanding of the causal and formal aspects of development and are beginning to forge essential, strong bonds between molecular biologists and clinicians in a mutually supportive discipline of developmental biology. However, to grieving parents of a stillborn fetus with, say, Pentalogy of Cantrell, sirenomelia or otocephaly, mouse data offer little comfort or reassurance about recurrence; thus, it is imperative to make ever more effective a science of human teratology (sensu lato) with participating reproductive geneticists, obstetricians, neonatologists, ultrasonographers, pediatric/fetal pathologists, cytogeneticists and pediatric geneticists to generate the diagnostic, pathogenetic and causal data necessary to counsel and to comfort the parents. Few molecular data exist on causes of blastogenetic defects in humans; however, the phenomenon of parsimony, whereby the same "morphogenetic" molecule, say, sonic hedgehog (SHH), is "deployed" simultaneously or sequentially during the morphogenesis (and even the histogenesis) of several/many embryonic primordia, makes it likely that a genetic/epigenetic disturbance of such an inductive system will have multiple effects on blastogenetic, organogenetic and perhaps also histogenetic events in the embryo. If causally defined, such a pattern of anomalies constitutes pleiotropy, and the embryo/fetus can be said to have a syndrome. If cause is unknown, the presumption of pleiotropy is less certain, and the fetus/infant may be said to have an "association" with low empiric recurrence risk.

Urorectal septum malformation sequence: Insights into pathogenesis

We characterize the urorectal septum malformation sequence (URSMS) in discordant fetal lambs and relate it to the human syndromes with which URSMS is associated. We found abnormal external genitalia, imperforate anus, and fistulous connections between the rectum, bladder, and vagina. Discordance among the dizygous twins eliminated teratogens as a likely etiologic factor. We summarize the relevant literature and propose a molecular model for the pathogenesis of the URSMS, in which alterations in sonic hedgehog and homeobox genes lead to caudal mesodermal deficiency during blastogenesis.

Caudal regression syndrome versus sirenomelia: a case report

We describe a newborn with clinical features of sirenomelia including fused lower limbs with medial position, absence of fibula, anal atresia, bilateral renal agenesis, and a single large umbilical artery. Recent literature describing the etiology of sirenomelia and relationship to caudal regression syndrome is reviewed.

Combination of renal agenesis with respiratory and alimentary tract atresia results in normal lung development

The VACTERL complex comprises renal agenesis and atresias of the alimentary and respiratory tracts. We report on a case with this combination causing severe oligohydramnios but with normal lung development. The likely protective mechanism for pulmonary development was an increase in alveolar pressure and reduced alveolar fluid loss due to the esophageal-tracheal malformation. This suggests the possible treatment of oligohydramnios by tracheal occlusion.

Bi-iliac distance and iliac bone position compared to the vertebral column in normal fetal development

Prenatal standards of bi-iliac width were not found in the literature based on autopsy investigations, nor was the caudo-cranial position of the ilia compared to the vertebral column. The first purpose of the present study was to establish normal standard values for the bi-iliac distance in fetal life, the second to evaluate the level of the iliac bones proportional to the ossified vertebral column. Whole body radiographs in antero-posterior projections from 98 human fetuses (36 female and 44 male fetuses, as well as 18 fetuses on which the sex had not been determined) were analyzed in the study. The fetuses derived from spontaneous or induced abortions and they were radiographed as part of the required autopsy procedure. The crown-rump-length (CRL) of the fetuses varied from 32 to 245 mm. The outer and inner bi-iliac distance was measured from the radiographs with a digital Helios slide caliper. The caudo-cranial position of the iliac bones was evaluated. The present study shows that in normal fetal development there is a continuous linear enlargement of the pelvic region in the transverse and vertical planes. The upper iliac contour stays at the level of the first sacral vertebral body, whereas the lower iliac line moves caudally. Significant differences between male and female fetuses were not found. The value of the present study is that the results can be used as reference standards in prenatal pathology.

Detection of Jarcho-Levin syndrome at 12 weeks' gestation by nuchal translucency screening and three-dimensional ultrasound

Jarcho-Levin syndrome (JLS) or spondylothoracic dysotosis causes early newborn death from respiratory insufficiency. Prenatal diagnosis is possible using fetal ultrasound, but requires a high level of suspicion and definitive diagnosis may be delayed well into the second trimester. We present a case in which a combination of three-dimensional ultrasound and measurement of nuchal translucency thickness allowed successful detection of recurrent JLS at 12 weeks' gestation.

Anal atresia, vertebral, genital, and urinary tract anomalies: a primary polytopic developmental field defect identified through an epidemiological analysis of associations

Anal atresia (AA) is observed per se or as part of different Mendelian or chromosomal syndromes, and as part of the VACTERL primary developmental field, CHARGE association, cloacal extrophy, in a mitochondrial cytopathy, and other multiple congenital anomaly patterns. There are only a few studies on the defects associated with AA, and in all of them it was observed that genitourinary defects are most frequent in infants with AA. Here we present the analysis of 28,410 malformed infants to study the frequency of 11 selected congenital defects in infants with AA in relation to their frequency in infants with multiple congenital anomaly patterns without AA. We conclude that the association of AA + spine defects + renal/urinary tract defects + genital defects constitutes a group of defects that tends to be present together in the same child because they are pathogenetically related, and since they are of blastogenetic origin they constitute a primary polytopic developmental field defect.