Sirenomelia: An anatomical assessment and genetic sex determination of two cases.

The etiology of sirenomelia is currently unknown. Data are limited in comparing external and internal abnormalities using modern imaging technologies and molecular genetic analysis. The purpose of the current study was designed to compare external and internal anatomical defects in two cases of sirenomelia and Potter's sequence. Considered rare, Potter's sequence is a fetal disorder with characteristic features of bilateral renal agenesis, obstructive uropathy, atypical facial appearance, and limb malformations. The internal and external malformations of two term fetuses with sirenomelia and Potter's sequence were compared using assessment of external features, radiography and MRI on internal structures, and molecular genetic studies on sex determination. Data reveal that both fetuses were male and manifested with an overlapping but distinct spectrum of abnormalities. Principal differences were noted in the development of the ears, brain, urogenital system, lower limbs, pelvis, and vertebral column. Defects of the axial mesoderm are likely to underlie the abnormalities seen in both fetuses. The first one, which had only caudal defects, was found to have a spectrum of abnormalities most similar to those associated with more severe forms of the small pelvic outlet syndrome, although the structure and orientation of the sacrum and iliae were different from previously reported cases. The other had both caudal and cranial defects, and was most similar to those described in the axial mesodermal dysplasia syndrome. Defects associated with sirenomelia can be evaluated with standard gross anatomy examination, radiology, MRI, and modified PCR techniques to determine anatomical abnormalities and the sex of preserved specimens, respectively. Evidence indicated that sirenomelia could be developed via various etiologies.

"Laurin-Sandrow Syndrome - a review of the literature and classification system".

INTRODUCTION: Laurin-Sandrow syndrome also known as tetramelic mirror-image polydactyly is a rare congenital disorder characterized classically by polysyndactyly of the hands, mirror feet and nose anomalies (hypoplasia of the nasal alae and short columella) often associated with ulnar and/or fibular duplication. As a pathologic entity, it is heterogeneous, the patients displaying a variety of symptoms. This review aims to analyze the different aspects of the condition, such as clinical findings and methods of treatment to summarize the principal features of Laurin-Sandrow syndrome. MATERIALS AND METHODS: The review is based on searches on PubMed, Web of Science and Researchgate of the following terms: "Laurin-Sandrow syndrome", "mirror hands", "mirror feet", "tetramelic mirror-image polydactyly", "fibular dimelia" and "ulnar dimelia". Clinical cases, reviews and original articles were included. RESULTS: As a consequence of our findings, we suggest a modification of the Al-Qattan classification system for Mirror Hand-Multiple Hand Spectrum. CONCLUSION: Even though it has an extremely low incidence, a thorough understanding of the syndrome enables the surgeon to choose the appropriate treatment with the ultimate goal to improve the patient's life quality.

Genetically induced redox stress occurs in a yeast model for Roberts syndrome.

Roberts syndrome (RBS) is a multispectrum developmental disorder characterized by severe limb, craniofacial, and organ abnormalities and often intellectual disabilities. The genetic basis of RBS is rooted in loss-of-function mutations in the essential N-acetyltransferase ESCO2 which is conserved from yeast (Eco1/Ctf7) to humans. ESCO2/Eco1 regulate many cellular processes that impact chromatin structure, chromosome transmission, gene expression, and repair of the genome. The etiology of RBS remains contentious with current models that include transcriptional dysregulation or mitotic failure. Here, we report evidence that supports an emerging model rooted in defective DNA damage responses. First, the results reveal that redox stress is elevated in both eco1 and cohesion factor Saccharomyces cerevisiae mutant cells. Second, we provide evidence that Eco1 and cohesion factors are required for the repair of oxidative DNA damage such that ECO1 and cohesin gene mutations result in reduced cell viability and hyperactivation of DNA damage checkpoints that occur in response to oxidative stress. Moreover, we show that mutation of ECO1 is solely sufficient to induce endogenous redox stress and sensitizes mutant cells to exogenous genotoxic challenges. Remarkably, antioxidant treatment desensitizes eco1 mutant cells to a range of DNA damaging agents, raising the possibility that modulating the cellular redox state may represent an important avenue of treatment for RBS and tumors that bear ESCO2 mutations.

Roberts syndrome in an Indian patient with humeroradial synostosis, congenital elbow contractures and a novel homozygous splice variant in ESCO2.

Roberts syndrome (also known as Roberts-SC phocomelia syndrome) is an autosomal recessive developmental disorder, characterized by pre- and postnatal growth retardation, limb malformations including bilateral symmetric tetraphocomelia or mesomelia, and craniofacial dysmorphism. Biallelic loss-of-function variants in ESCO2, which codes for establishment of sister chromatid cohesion N-acetyltransferase 2, cause Roberts syndrome. Phenotypic spectrum among patients is broad, challenging clinical diagnosis in mildly affected individuals. Here we report a 3-year-old boy with a mild phenotype of Roberts syndrome with bilateral elbow contractures, humeroradial synostosis, mild lower limb disparity, and facial dysmorphism. Trio whole-exome sequencing identified the novel biallelic splice variant c.1673+1G>A in ESCO2 in the patient. Aberrant ESCO2 pre-mRNA splicing, reduced relative ESCO2 mRNA amount, and characteristic cytogenetic defects, such as premature centromere separation, heterochromatin repulsion, and chromosome breaks, in patient cells strongly supported pathogenicity of the ESCO2 variant affecting one of the highly conserved guanine-thymine dinucleotide of the donor splice site. Our case highlights the difficulty in establishing a clinical diagnosis in individuals with minor clinical features of Roberts syndrome and normal intellectual and social development. However, next-generation sequencing tools allow for molecular diagnosis in cases presenting with mild developmental defects.

Sirenomelia (Mermaid Syndrome): A Case Report.

Sirenomelia, which is also known as mermaid syndrome and characterized by the fusion of the lower extremities, is the most severe form of caudal regression syndrome and one of the rare and lethal congenital malformations. The anomalies that might be seen in this syndrome include pelvic-sacral dysplasia, genital anomalies, bilateral pelvic renal fusion accompanied by renal dysplasia, colon atresia, unilateral umbilical artery, and imperforated anus. The incidence of sirenomelia is 0.8-1 cases in 60,000-100,000 deliveries and the male/female ratio is 2.7-3:1. The case reported in the present study was a 13-week-old male fetus 30 g in weight with a macerated appearance. The upper extremities had a relatively normal appearance but the lower extremities were conjoined and there was a single lower extremity consisting of conjoined feet and toes. In the face, the nasal bridge was sunken, the ears had a low position, and there were cleft palate and cleft lip. Examination of the external genital organs revealed that the penile part was in the anal region. There was no anus opening. The crown-rump length was 8.5cm, the heel-toe length was approx. 1cm, and the rump-heel length was approx. 3.7cm. There were none of the two kidneys, ureter, bladder, urethra, or rectum. In the umbilical cord, there were 2 venous structures, one of which was the artery. Perivillous congestion and hyperemia, perivillous calcification, deciduitis, and focal infarct regions were observed in placental tissues. This report aims to discuss this very rare case together with the literature.

Non-redundant roles in sister chromatid cohesion of the DNA helicase DDX11 and the SMC3 acetyl transferases ESCO1 and ESCO2.

In a process linked to DNA replication, duplicated chromosomes are entrapped in large, circular cohesin complexes and functional sister chromatid cohesion (SCC) is established by acetylation of the SMC3 cohesin subunit. Roberts Syndrome (RBS) and Warsaw Breakage Syndrome (WABS) are rare human developmental syndromes that are characterized by defective SCC. RBS is caused by mutations in the SMC3 acetyltransferase ESCO2, whereas mutations in the DNA helicase DDX11 lead to WABS. We found that WABS-derived cells predominantly rely on ESCO2, not ESCO1, for residual SCC, growth and survival. Reciprocally, RBS-derived cells depend on DDX11 to maintain low levels of SCC. Synthetic lethality between DDX11 and ESCO2 correlated with a prolonged delay in mitosis, and was rescued by knockdown of the cohesin remover WAPL. Rescue experiments using human or mouse cDNAs revealed that DDX11, ESCO1 and ESCO2 act on different but related aspects of SCC establishment. Furthermore, a DNA binding DDX11 mutant failed to correct SCC in WABS cells and DDX11 deficiency reduced replication fork speed. We propose that DDX11, ESCO1 and ESCO2 control different fractions of cohesin that are spatially and mechanistically separated.

Homozygous Null TBX4 Mutations Lead to Posterior Amelia with Pelvic and Pulmonary Hypoplasia.

The development of hindlimbs in tetrapod species relies specifically on the transcription factor TBX4. In humans, heterozygous loss-of-function TBX4 mutations cause dominant small patella syndrome (SPS) due to haploinsufficiency. Here, we characterize a striking clinical entity in four fetuses with complete posterior amelia with pelvis and pulmonary hypoplasia (PAPPA). Through exome sequencing, we find that PAPPA syndrome is caused by homozygous TBX4 inactivating mutations during embryogenesis in humans. In two consanguineous couples, we uncover distinct germline TBX4 coding mutations, p.Tyr113∗ and p.Tyr127Asn, that segregated with SPS in heterozygous parents and with posterior amelia with pelvis and pulmonary hypoplasia syndrome (PAPPAS) in one available homozygous fetus. A complete absence of TBX4 transcripts in this proband with biallelic p.Tyr113∗ stop-gain mutations revealed nonsense-mediated decay of the endogenous mRNA. CRISPR/Cas9-mediated TBX4 deletion in Xenopus embryos confirmed its restricted role during leg development. We conclude that SPS and PAPPAS are allelic diseases of TBX4 deficiency and that TBX4 is an essential transcription factor for organogenesis of the lungs, pelvis, and hindlimbs in humans.

Sirenomelia and maternal chlamydia trachomatis infection: a case report and review.

Background: Sirenomelia is a lethal congenital anomaly, presenting with fusion of lower extremities and malformed perineum. The pathogenesis is unclear, and "defective blastogenesis" is the proposed mechanism. Chlamydia trachomatis (CT) is an obligate intracellular pathogen which reportedly invades placenta and may result in fetal demise. It has documented cytopathogenic effects, specifically, cellular disruption, tissue dysgenesis, and genomic instability.Case report: An infant with sirenomelia was born as a product of 30 weeks of pregnancy, which was normal except for a persistent maternal CT infection. The infant expired shortly after birth.Conclusion: Fetal invasion by CT, conceivably, may induce structural anomalies, such as sirenomelia by virtue of its cytopathic effects. We intend to draw attention to such a possibility by reporting this case. This association, however, is speculative and more cases of sirenomelia with CT positive mothers need to be described in order to make definite conclusions about such a relationship.

Clinical spectrum of congenital tibial hemimelia in 35 limbs of 24 patients: A single center observational study from India.

PURPOSE: Considering the paucity of reports on large series of patients with tibial hemimelia, we assessed the clinical spectrum of this rare congenital disorder in patients seen at a single Indian center over 10 years. METHODS: Retrospective review of medical records of patients seen at single center in 10 years. RESULTS: Thirty-five cases of TH, mostly Jones types Ia (18) and II (10), were diagnosed in 24 patients (13 had unilateral TH). Associated foot deformities included equinovarus (22), varus foot (10), absence of the medial row of toes (5) and polydactyly (3). Upper limbs anomalies included split-hand deformity (five patients) and radial club hand (two patients). Nine limbs of seven patients were surgically reconstructed. Modified orthosis was provided to seven patients, custom designed prosthesis fitment in six and amputation with prosthesis fitment in one. Patients presenting at adolescence or later were habituated to their deformity for indoor ambulation; families declined amputation. CONCLUSION: Reports of more TH cases will provide input to researchers to consider comprehensive rehabilitation for enhancing indoor and community ambulation.

Effects of the Y-chromosome and the dominant hemimelia mutation on the morphology of the mouse mandible.

The aims of this study were to test whether the Y-chromosome and the autosomal dominant hemimelia (Dh) mutation can affect mandible morphology in mice. I analyzed mandible size and shape using landmark-based geometric morphometrics in 16 DH-Chr Y@ -+/+ (@ represents one of the inbred strain names) strains and observed significant differences in mandible size. The largest mandible was identified in strain DH-Chr YC3H and the smallest in strain DH-Chr YKK . Canonical variate and discriminant function analyses suggested that the mandible shapes of strains DH-Chr YC3H and DH-Chr YKK differed from those of the other strains. Because seven of the DH-Chr Y@ -+/+ strains were maintained with dominant hemimelia, I also analyzed the potential influence of dominant hemimelia on mandible morphology because dominant hemimelia is known to cause various skeletal malformations. There were no significant differences in mandible size in seven sets of DH-Chr Y@ -+/+ and DH-Chr Y@ -Dh/+ strains. However, canonical variate analysis mapped strains DH-Chr YCAS -Dh/+ and DH-Chr YCBA -Dh/+ mapped distantly from the rest. Additionally, I observed similar patterns of shape change between DH-Chr YCAS -+/+ and DH-Chr YCAS -Dh/+, and between DH-Chr YCBA -+/+ and DH-Chr YCBA -Dh/+. These data indicate that the Y-chromosome affects the size and shape of the mouse mandible. Dominant hemimelia affects mandible shape but not size, and its effects emerge depending on the kinds of Y-chromosomes.

Developmental toxicity of flucytosine following administration to pregnant rats at a specific time point of organogenesis.

To investigate the abnormalities that are specific to administration of flucytosine at one time point during embryonic organogenesis, flucytosine was administered orally to pregnant Sprague Dawley (SD) rats in a single dose on day 11 of pregnancy at 25 or 35 mg/kg. Fetuses on day 20 of pregnancy were externally, viscerally, and skeletally examined. Maternal body weight gain and food consumption were suppressed the day after administration of a 35 mg/kg. Fetal examinations revealed various alterations in both dose groups: externally preaxial polydactyly in the hind limb; skeletally fused lumbar centrum, absent sacral centrum, supernumerary sacral vertebra, and absent ribs. Our findings indicated that specific types of external and skeletal anomalies were induced following flucytosine administration on day 11 of pregnancy.

A Roberts Syndrome Individual With Differential Genotoxin Sensitivity and a DNA Damage Response Defect.

PURPOSE: Roberts syndrome (RBS) is a rare, recessively transmitted developmental disorder characterized by growth retardation, craniofacial abnormalities, and truncation of limbs. All affected individuals to date have mutations in the ESCO2 (establishment of cohesion 2) gene, a key regulator of the cohesin complex, which is involved in sister chromatid cohesion and DNA double-strand break (DSB) repair. Here we characterize DNA damage responses (DDRs) for the first time in an RBS-affected family. METHODS AND MATERIALS: Lymphoblastoid cell lines were established from an RBS family, including the proband and parents carrying ESCO2 mutations. Various DDR assays were performed on these cells, including cell survival, chromosome break, and apoptosis assays; checkpoint activation indicators; and measures of DNA breakage and repair. RESULTS: Cells derived from the RBS-affected individual showed sensitivity to ionizing radiation (IR) and mitomycin C-induced DNA damage. In this ESCO2 compound heterozygote, other DDRs were also defective, including enhanced IR-induced clastogenicity and apoptosis; increased DNA DSB induction; and a reduced capacity for repairing IR-induced DNA DSBs, as measured by γ-H2AX foci and the comet assay. CONCLUSIONS: In addition to its developmental features, RBS can be, like ataxia telangiectasia, considered a DDR-defective syndrome, which contributes to its cellular, molecular, and clinical phenotype.

Limb body wall complex: Its delineation and relationship with amniotic bands using clustering methods.

BACKGROUND: Despite the numerous reports on the limb body wall complex (LBWC), this association has never been adequately defined. Amniotic bands (AB) are frequently present but their role remains unclear. Since most reports were based on clinical and often subjective diagnoses, the aim of this work was to define LBWC and the role of AB, minimizing subjectivity. METHODS: Data were obtained from the ECLAMC maternity hospitals network database. A total of 450 live and stillborn infants, born during 1967-2013, with AB or the LBWC were selected. A hierarchical cluster analysis was used to classify cases into homogeneous groups (sharing similar associated defects); robustness of the classification was confirmed with a discriminant analysis. The frequency of associated defects was compared among groups; those whose frequency differed significantly were included in a logistic regression to establish their association within each group. RESULTS: The cluster analysis identified two groups: a body wall defect (BWD) predominating in one, AB in the other. These groups were further divided into: BWD (cases with only BWD), AB (with only AB), BWD + AB, and NONE (with neither). Association with caudal defects and lower limb amelia was observed for BWD, with cephalic defects and upper limb amputations for BWD + AB. CONCLUSIONS: The results, obtained with the least possible subjectivity, indicated that BWD and BWD + AB are different conditions. Since BWD specifically associates with amelia, we propose that this defect and not any limb deficiency should be considered as inclusion criterium and that it should be included in the BWD acronym as LBWC.

Hypopigmented patches in Roberts/SC phocomelia syndrome occur via aneuploidy susceptibility.

Roberts/SC phocomelia syndrome (RBS/SC) is a rare autosomal recessive inherited condition characterized by prenatal-onset growth retardation, craniofacial anomalies, and symmetrical limb reduction defects. Here, we present two affected siblings with RBS/SC who have consanguineous parents. Both patients had intrauterine growth retardation; similar facial findings, including arched eyebrows, epicanthic folds, posteriorly angulated ears, and retrognathia; and hypopigmented patches on their skin. However, despite these common findings, the extremity involvement was different between the patients. The more severely affected boy had hypoplasia of the tibia and symmetrical agenesis of the radius, ulna, proximal carpal bones, and fibula. The slightly affected girl presented with mild symmetrical mesomelic shortening. The cytogenetic analysis showed aneuploidies at varying rates concerning different chromosomes in the analyses of different culture materials. As a remarkable finding in the cytogenetic studies, chromosome analysis of fibroblast cultures obtained from the hypopigmented skin region showed a much higher frequency of aneuploidy, especially trisomy 7, than normopigmented skin fibroblasts and lymphocyte cultures for both patients, which was also proven ex vivo by qPCR analyses from uncultured skin tissues. In the subsequent ESCO2 gene sequence analysis, both patients were found to be homozygous for the mutation c.1111dupA (p.Thr371Asnfs*32; NM_001017420.2), which is known to be pathogenic. In the literature search, only two RBS/SC patient reports with hypopigmented skin patches could be found. In addition, the presence of pigmentation defects in the embryo was reported in some different animal models for RBS/SC. When the literature review and study are evaluated together, hypopigmented patches can be considered as a rare finding for RBS/SC. It can be suggested that somatic aneuploidies seen in the natural course of the disease, especially aneuploidy of chromosome 7, which has many genes associated with pigmentation, may be responsible for the hypopigmentation patches.

Ankle reconstruction and lengthening strategy in type II fibular hemimelia: a report of two cases.

Limb lengthening of fibular hemimelia is associated with progressive ankle valgus deformity. We reported a successful tibial lengthening in fibular hemimelia without recurrence of ankle valgus in 2 cases. The procedure involved 2 stages. First stage was a resection of the fibular remnant followed by a bending osteotomy through the distal tibial physis before the age of 2 years old. The second stage was a tibia lengthening up to 25% of its original segmental length performed at the age of 5 years old. There was neither progressive ankle valgus nor distal tibial growth arrest observed at 4 years follow-up.

An unnoticed variant of Sirenomelia with constellation of multiple anomalies

Sirenomelia is a rare fatal congenital anomaly, characterized by a single midline lower limb, urogenital anomalies, Potter's facies and a single umbilical artery. Approximately 400 cases have been reported in the literature. Based on the number of feet and the degree of lower limb bone fusion, it is classified into seven different types. Sirenomelia has been reported with associated anomalies involving multiple systems mainly of urogenital, respiratory as well as the alimentary tract system. In the present case, the authors reported an unnoticed variation in the fusion of lower limbs and its rare association with tracheoesophageal fistula

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Postaxial limb hypoplasia (PALH): the classification, clinical features, and related developmental biology.

Postaxial limb hypoplasia (PALH) is a group of nonhereditary diseases with congenital lower limb deficiency affecting the fibular ray, including fibular hemimelia, proximal femoral focal deficiency, and tarsal coalition. The etiology and the developmental biology of the anomaly are still not fully understood. Here, we review the previous classification systems, present the clinical features, and discuss the developmental biology of PALH.

Repeated removal of developing limb buds permanently reduces appendage size in the highly-regenerative axolotl.

Matching appendage size to body size is fundamental to animal function. Generating an appropriately-sized appendage is a robust process executed during development which is also critical for regeneration. When challenged, larger animals are programmed to regenerate larger limbs than smaller animals within a single species. Understanding this process has important implications for regenerative medicine. To approach this complex question, models with altered appendage size:body size ratios are required. We hypothesized that repeatedly challenging axolotls to regrow limb buds would affect their developmental program resulting in altered target morphology. We discovered that after 10 months following this experimental procedure, limbs that developed were permanently miniaturized. This altered target morphology was preserved upon amputation and regeneration. Future experiments using this platform should provide critical information about how target limb size is encoded within limb progenitors.

Chromatin determinants of the inner-centromere rely on replication factors with functions that impart cohesion.

Replication fork-associated factors promote genome integrity and protect against cancer. Mutations in the DDX11 helicase and the ESCO2 acetyltransferase also cause related developmental disorders classified as cohesinopathies. Here we generated vertebrate model cell lines of these disorders and cohesinopathies-related genes. We found that vertebrate DDX11 and Tim-Tipin are individually needed to compensate for ESCO2 loss in chromosome segregation, with DDX11 also playing complementary roles with ESCO2 in centromeric cohesion. Our study reveals that overt centromeric cohesion loss does not necessarily precede chromosome missegregation, while both these problems correlate with, and possibly originate from, inner-centromere defects involving reduced phosphorylation of histone H3T3 (pH3T3) in the region. Interestingly, the mitotic pH3T3 mark was defective in all analyzed replication-related mutants with functions in cohesion. The results pinpoint mitotic pH3T3 as a postreplicative chromatin mark that is sensitive to replication stress and conducts with different kinetics to robust centromeric cohesion and correct chromosome segregation.