A homeobox gene, HLXB9, is the major locus for dominantly inherited sacral agenesis

Aberrant MNX1 expression associated with t(7;12)(q36;p13) pediatric acute myeloid leukemia induces the disease through altering histone methylation

Certain subtypes of acute myeloid leukemia (AML) in children have inferior outcome, such as AML with translocation t(7;12)(q36;p13) leading to an MNX1::ETV6 fusion along with high expression of MNX1. We have identified the transforming event in this AML and possible ways of treatment. Retroviral expression of MNX1 was able to induce AML in mice, with similar gene expression and pathway enrichment to t(7;12) AML patient data. Importantly, this leukemia was only induced in immune incompetent mice using fetal but not adult hematopoietic stem and progenitor cells. The restriction in transforming capacity to cells from fetal liver is in alignment with t(7;12)(q36;p13) AML being mostly seen in infants. Expression of MNX1 led to increased histone 3 lysine 4 mono-, di- and trimethylation, reduction in H3K27me3, accompanied with changes in genome-wide chromatin accessibility and genome expression, likely mediated through MNX1 interaction with the methionine cycle and methyltransferases. MNX1 expression increased DNA damage, depletion of the Lin-/Sca1+/c-Kit+ population and skewing toward the myeloid lineage. These effects, together with leukemia development, were prevented by pre-treatment with the S-adenosylmethionine analog Sinefungin. In conclusion, we have shown the importance of MNX1 in development of AML with t(7;12), supporting a rationale for targeting MNX1 and downstream pathways.

Molecular landscape of congenital vertebral malformations: recent discoveries and future directions

Vertebral malformations (VMs) pose a significant global health problem, causing chronic pain and disability. Vertebral defects occur as isolated conditions or within the spectrum of various congenital disorders, such as Klippel-Feil syndrome, congenital scoliosis, spondylocostal dysostosis, sacral agenesis, and neural tube defects. Although both genetic abnormalities and environmental factors can contribute to abnormal vertebral development, our knowledge on molecular mechanisms of numerous VMs is still limited. Furthermore, there is a lack of resource that consolidates the current knowledge in this field. In this pioneering review, we provide a comprehensive analysis of the latest research on the molecular basis of VMs and the association of the VMs-related causative genes with bone developmental signaling pathways. Our study identifies 118 genes linked to VMs, with 98 genes involved in biological pathways crucial for the formation of the vertebral column. Overall, the review summarizes the current knowledge on VM genetics, and provides new insights into potential involvement of biological pathways in VM pathogenesis. We also present an overview of available data regarding the role of epigenetic and environmental factors in VMs. We identify areas where knowledge is lacking, such as precise molecular mechanisms in which specific genes contribute to the development of VMs. Finally, we propose future research avenues that could address knowledge gaps.

Treatment Strategy for Currarino Syndrome Complicated With Anorectal Stenosis

PURPOSE

The present study aimed to review the treatment experience and outcomes of Currarino syndrome (CS) complicated with anorectal stenosis to evaluate the current treatment strategies.

METHODS

Seven cases of CS complicated with anorectal stenosis, treated at our hospital between 1998 and 2021, were retrospectively investigated. This is a case series article from a single institution.

RESULTS

In six and three cases and one case, the presacral mass was a mature teratoma, meningocele, and lipoma, respectively. Resection of the lesion was performed in all six cases of mature teratoma, and duraplasty was performed before resection in all three cases of meningocele. Moreover, surgery for anorectal stenosis was performed simultaneously in four patients. Surgery was performed for six cases of anorectal stenosis, with the remaining case relieved by dilation using a metal bougie. The surgical methods used were a partial resection with end-to-end anastomosis, anorectal strictureplasty, pull-through, posterior sagittal anorectoplasty, and cutback after mass resection. Pathological analysis of the anorectal stenoses revealed disorganized and rough smooth muscle fibers and the replacement of the stroma by an increased quantity of collagen fibers.

CONCLUSIONS

The clinical outcomes of CS can be improved by establishing a treatment flow chart and understanding the complicated pathophysiology of the disease.

Sacral agenesis without maternal diabetes: a case report

Introduction

Sacral agenesis is a rare congenital condition that is characterized by sacrococcygeal bone agenesis. It is associated with spinal cord anomalies as well as problems with the genitourinary system, large bowel, and lower extremities. Fetal ultrasound allows for diagnosis even before birth.

Case presentation

The authors present the case of a 1-year-old girl with sacral agenesis type III and bilateral congenital talipes equinovarus with spina bifida who was born to a nondiabetic mother and had a normal anomaly scan.

Clinical discussion

People with less severe forms of sacral agenesis can live a normal life, and it is not connected with cognitive impairment; however, concomitant bladder, colon, and lower limb disorders cause considerable morbidity. The majority of treatment is supportive, frequently requiring orthopedic, urological, gastroenterological, pediatric, and physiotherapy support.

Conclusion

Genetic and prepregnancy counseling, as well as early screening of high-risk mothers, remain the only options for prevention of the disease since treatment is mostly supportive.

Caudal Regression Syndrome-A Narrative Review: An Orthopedic Point of View

Abnormalities in cellular differentiation during embryo-fetal period may lead to various malformations of the spine. Caudal regression syndrome (CRS) is a group of defects with premature growth/development termination of the vertebral column. CRS can be divided into three types: sirenomelia, complete absence of the sacrum and partial absence of the sacrum. Genitourinary and gastrointestinal anomalies are common, with neurogenic bladder and bowel incontinence. Treatment of patients with CRS is complex and multidisciplinary and should be comprehensive. The most common orthopedic problems are: spinal deformity (kyphosis and scoliosis), spinopelvic instability and lower limbs deformities.

Embryology and anatomy of anorectal malformations

The etiology of anorectal malformations (ARM) is complicated because of the spectrum of anomalies seen clinically, many of which are isolated and seemingly unique. Recent studies suggest that ARMs result from abnormal cloacal membrane (CM) development that contributes to disrupt normal local muscle and nerve development. If CM maldevelopment is severe, the rectal pouch lies above the pelvic floor, resulting in asymmetric and/or deviated musculature, so a midline incision is likely to cause trauma or be detrimental. Autonomic nerve plexuses can be associated with a fistula tract in ARMs and are also at risk for damage during surgery and contribute to genitourinary complications. Understanding the anatomy and development of the perineum is crucial for treating the broad spectrum of anomalies associated with ARMs and may assist in predicting/managing other related morbidity.

Case report of experience of misdiagnosis of Currarino syndrome as ovarian cyst

The medical information was collected for Currarino syndrome. The patient had anal surgery for congenital anal stenosis when 2 years old. Clinical manifestations were pelvic cystic mass and low abdominal pain. The pelvic mass was found with a diameter of about 20 cm during the transabdominal exploration. At the second day after operation, the patient complained of neck pain. Neurosurgeon performed surgical treatment and diagnosed it as anterior sacral meningocoele. Currarino syndrome has female pelvic mass, sacral malformation, and congenital anorectal malformation, blindly puncture or drainage before operation should not be permitted.

Towards clinical applications of in vitro-derived axial progenitors

The production of the tissues that make up the mammalian embryonic trunk takes place in a head-tail direction, via the differentiation of posteriorly-located axial progenitor populations. These include bipotent neuromesodermal progenitors (NMPs), which generate both spinal cord neurectoderm and presomitic mesoderm, the precursor of the musculoskeleton. Over the past few years, a number of studies have described the derivation of NMP-like cells from mouse and human pluripotent stem cells (PSCs). In turn, these have greatly facilitated the establishment of PSC differentiation protocols aiming to give rise efficiently to posterior mesodermal and neural cell types, which have been particularly challenging to produce using previous approaches. Moreover, the advent of 3-dimensional-based culture systems incorporating distinct axial progenitor-derived cell lineages has opened new avenues toward the functional dissection of early patterning events and cell vs non-cell autonomous effects. Here, we provide a brief overview of the applications of these cell types in disease modelling and cell therapy and speculate on their potential uses in the future.

Exome sequencing identifies variants in infants with sacral agenesis

BACKGROUND

Sacral agenesis (SA) consists of partial or complete absence of the caudal end of the spine and often presents with additional birth defects. Several studies have examined gene variants for syndromic forms of SA, but only one has examined exomes of children with non-syndromic SA.

METHODS

Using buccal cell specimens from families of children with non-syndromic SA, exomes of 28 child-parent trios (eight with and 20 without a maternal diagnosis of pregestational diabetes) and two child-father duos (neither with diagnosis of maternal pregestational diabetes) were exome sequenced.

RESULTS

Three children had heterozygous missense variants in ID1 (Inhibitor of DNA Binding 1), with CADD scores >20 (top 1% of deleterious variants in the genome); two children inherited the variant from their fathers and one from the child's mother. Rare missense variants were also detected in PDZD2 (PDZ Domain Containing 2; N = 1) and SPTBN5 (Spectrin Beta, Non-erythrocytic 5; N = 2), two genes previously suggested to be associated with SA etiology. Examination of variants with autosomal recessive and X-linked recessive inheritance identified five and two missense variants, respectively. Compound heterozygous variants were identified in several genes. In addition, 12 de novo variants were identified, all in different genes in different children.

CONCLUSIONS

To our knowledge, this is the first study reporting a possible association between ID1 and non-syndromic SA. Although maternal pregestational diabetes has been strongly associated with SA, the missense variants in ID1 identified in two of three children were paternally inherited. These findings add to the knowledge of gene variants associated with non-syndromic SA and provide data for future studies.

Genetic Counseling and Diagnostics in Anorectal Malformation

Anorectal malformation (ARM) is a relatively frequently occurring congenital anomaly of hindgut development with a prevalence of 1 in 3,000 live births. ARM may present as an isolated anomaly, but it can also be associated with other anomalies, sometimes as part of a recognizable syndrome. After birth, much medical attention is given to the treatment and restoring of bowel function in children with ARM. Effort should also be given to studying the etiology of the ARM in these patients. This information is important to both the medical community and the family, because it can help guide treatment and provides information on the long-term prognosis of the patient and recurrence risk in the family.In this article, we will review the current knowledge on the (genetic) etiology of (syndromic) ARM and provide guidelines for (family) history taking and clinical and genetic studies of ARM patients and their families, which is needed to study the causal factors in an ARM patient and for genetic counseling of the families.

Complete lung agenesis caused by complex genomic rearrangements with neo-TAD formation at the SHH locus

During human organogenesis, lung development is a timely and tightly regulated developmental process under the control of a large number of signaling molecules. Understanding how genetic variants can disturb normal lung development causing different lung malformations is a major goal for dissecting molecular mechanisms during embryogenesis. Here, through exome sequencing (ES), array CGH, genome sequencing (GS) and Hi-C, we aimed at elucidating the molecular basis of bilateral isolated lung agenesis in three fetuses born to a non-consanguineous family. We detected a complex genomic rearrangement containing duplicated, triplicated and deleted fragments involving the SHH locus in fetuses presenting complete agenesis of both lungs and near-complete agenesis of the trachea, diagnosed by ultrasound screening and confirmed at autopsy following termination. The rearrangement did not include SHH itself, but several regulatory elements for lung development, such as MACS1, a major SHH lung enhancer, and the neighboring genes MNX1 and NOM1. The rearrangement incorporated parts of two topologically associating domains (TADs) including their boundaries. Hi-C of cells from one of the affected fetuses showed the formation of two novel TADs each containing SHH enhancers and the MNX1 and NOM1 genes. Hi-C together with GS indicate that the new 3D conformation is likely causative for this condition by an inappropriate activation of MNX1 included in the neo-TADs by MACS1 enhancer, further highlighting the importance of the 3D chromatin conformation in human disease.

The Role of De Novo Variants in Formation of Human Anorectal Malformations

Anorectal malformations (ARM) represent a rare birth defect of the hindgut that occur in approximately 1 in 3000 live births. Around 60% of ARM occur with associated anomalies including defined genetic syndromes and associations with chromosomal aberrations. The etiology of ARM is heterogeneous, with the individual environmental or genetic risk factors remaining unknown for the majority of cases. The occurrence of familial ARM and previous epidemiologic analysis suggest autosomal dominant inheritance in a substantial subset of ARM patients. The implicated mortality and reduced fecundity in patients with ARM would lead to allele loss. However, mutational de novo events among the affected individuals could compensate for the evolutionary pressure. With the implementation of exome sequencing, array-based molecular karyotyping and family-based rare variant analyses, the technologies are available to identify the respective factors. This review discusses the identification of disease-causing variants among individuals with ARM. It highlights the role of mutational de novo events.

The first case of mosaic MNX1 mutation in an adult female with features of Currarino syndrome

BACKGROUND

Currarino syndrome (CS) is a rare genetic condition characterized by the association of three major clinical signs: anorectal malformation (ARM), sacro-coccygeal bone defects, and presacral mass. Different kinds of ARM can be present such as anteriorly placed anus, imperforate anus, anorectal stenosis, rectal duplication, and fistulae. The presacral mass can be a benign teratoma, a dermoid or neurenteric cyst, anterior meningocele or hamartoma. Females are more frequently affected and usually present with associated gynecologic and urinary tract problems. CS is considered an autosomal dominant trait, with reduced penetrance and variable expressivity. CS is associated with mutations in the MNX1 gene (motor neuron and pancreas homeobox-1, previously known as HLXB9) mapped to chromosome 7q36. Heterozygous loss-of-function mutations in the coding sequence of MNX1 gene have been reported in nearly all familial CS cases and in approximately 30% of CS sporadic patients.

CASE

Here, we present the case of a woman with features of CS carrying a mosaic mutation in the coding region of MNX1 gene. This is the only reported case of a CS diagnosis in which the mutation is present in less than 50% of cells.

CONCLUSION

The lower detection rate of MNX1 mutations in sporadic cases could similarly be explained by somatic mosaicism, mutations occurring outside the coding regions, or genetic heterogeneity.

Familial tendency in patients with lipoma of the filum terminale

PURPOSE

Lipoma of the filum terminale (FL) is an abnormality in which fat is deposited in the filum terminale. This lipoma is often detected by skin abnormalities in the lumbosacral area such as a sacrococcygeal dimple. Some cases may develop tethered cord and become symptomatic. However, the genetic basis of FL is still unclear.

METHODS

This study aimed to determine whether there was a family history of FL or other forms of spina bifida among 54 families of 56 patients with FL and to examine whether there is a familial predisposition in FL. In addition, sex, age at diagnosis, presence of symptoms, presence of sacrococcygeal dimple, and the level of conus medullaris between familial and spontaneous cases were evaluated.

RESULTS

Of the 54 families of FL patients, there were 48 siblings. Among the 48 siblings, 2 had "occult" FL. The frequency of FL among siblings was estimated to be 4.2% (2/48), which was significantly higher than the sum of previously reported cases of spontaneous FL (0.91%; p = 0.017). However, there was no significant difference in sex, age at diagnosis, presence of symptoms, presence of sacrococcygeal dimple, diameter of filum terminale, or level of conus medullaris between familial and spontaneous cases.

CONCLUSION

To our knowledge, this is the first report on familial FL and examination of the frequency of FL among siblings. The high probability of FL among siblings of FL patients suggests that genetic factors may play a role in FL development.

Currarino syndrome: a comprehensive genetic review of a rare congenital disorder

Background

The triad of a presacral mass, sacral agenesis and an anorectal anomaly constitutes the rare Currarino syndrome (CS), which is caused by dorsal–ventral patterning defects during embryonic development. The major causative CS gene is MNX1, encoding a homeobox protein.

Main body

In the majority of patients, CS occurs as an autosomal dominant trait; however, a female predominance observed, implies that CS may underlie an additional mode(s) of inheritance. Often, the diagnosis of CS is established solely by clinical findings, impacting a detailed analysis of the disease. Our combined data, evaluating more than 60 studies reporting patients with CS-associated mutations, revealed a slightly higher incidence rate in females with a female-to-male ratio of 1.39:1. Overall, MNX1 mutation analysis was successful in only 57.4% of all CS patients investigated, with no mutation detected in 7.7% of the familial and 68% of the sporadic patients. Our studies failed to detect the presence of an expressed MNX1 isoform that might explain at least some of these mutation-negative cases.

Conclusion

Aside from MNX1, other genes or regulatory regions may contribute to CS and we discuss several cytogenetic studies and whole-exome sequencing data that have implicated further loci/genes in its etiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01799-0.

Molecular mechanisms of β-cell dysfunction and death in monogenic forms of diabetes

Monogenetic forms of diabetes represent 1%-5% of all diabetes cases and are caused by mutations in a single gene. These mutations, that affect genes involved in pancreatic β-cell development, function and survival, or insulin regulation, may be dominant or recessive, inherited or de novo. Most patients with monogenic diabetes are very commonly misdiagnosed as having type 1 or type 2 diabetes. The severity of their symptoms depends on the nature of the mutation, the function of the affected gene and, in some cases, the influence of additional genetic or environmental factors that modulate severity and penetrance. In some patients, diabetes is accompanied by other syndromic features such as deafness, blindness, microcephaly, liver and intestinal defects, among others. The age of diabetes onset may also vary from neonatal until early adulthood manifestations. Since the different mutations result in diverse clinical presentations, patients usually need different treatments that range from just diet and exercise, to the requirement of exogenous insulin or other hypoglycemic drugs, e.g., sulfonylureas or glucagon-like peptide 1 analogs to control their glycemia. As a consequence, awareness and correct diagnosis are crucial for the proper management and treatment of monogenic diabetes patients. In this chapter, we describe mutations causing different monogenic forms of diabetes associated with inadequate pancreas development or impaired β-cell function and survival, and discuss the molecular mechanisms involved in β-cell demise.

Presacral neuroendocrine tumors associated with the Currarino syndrome

Currarino syndrome (CS) is an autosomal dominant syndrome caused by mutations in MNX1 and characterized by anorectal abnormalities, partial sacral agenesis, and presacral masses. The presacral masses are typically benign; however, malignant degeneration can occur, and presacral neuroendocrine tumors (NETs) have been reported in six cases. We report three individuals from two families affected by CS in which multiple individuals developed presacral NETs. The first family, 491, had six members with features of CS, including two siblings who presented with presacral, Grade 2 NETs, one of which had metastasized to bone and lymph nodes. A germline c.874C>T (p.Arg292Trp) mutation was found in a highly conserved region of MNX1 in three affected members who underwent sequencing. A second somatic variant/deletion in MNX1 was not detected in either patient's tumor. In the second family, 342, the proband presented with an incidentally discovered presacral NET. The proband's father had previously undergone resection of a presacral NET, and so genetic testing was performed, which did not reveal an MNX1 mutation or copy number variants. The lack of a second, somatic mutation in the tumors from family 491 argues against MNX1 acting as a tumor suppressor, and the absence of a germline MNX1 mutation in family 342 suggests that other genetic and anatomic factors contribute to the development of presacral NETs. These cases highlight the variable presentation of CS, and the potential for malignancy in these patients.

Impact of Rigid Fixation of the Pubic Symphysis for Spinopelvic Fixation in Two Cases of Lumbosacral Agenesis

Introduction

In patients with lumbosacral agenesis (SA), Renshaw type III or IV, lumbosacral instability is the primary cause of major clinical complications. Although they are usually treated with spinopelvic fusion, nonunion at the spinopelvic junction is a major complication due to the congenital sacropelvic abnormalities. The purpose of this study was to evaluate whether a combination of lumbosacral fixation and rigid fixation at the pubic symphysis could lead to postoperative bone union in patients with SA (Renshaw type III).

Methods

Retrospective case series study. We present the cases of two patients with SA, Renshaw type III, who were surgically treated by lumbosacral fusion using a posterior approach, and they exhibited nonunion at the lumbosacral junction.

Results

Case 1. A 10-year-old male underwent T8-S posterior fixation followed by multiple augmentations using allografts at the lumbosacral junction for delayed union. All additional procedures with bone graft using a posterior approach failed to achieve bone union; however, additional rigid fixation at the pubic symphysis resulted in a successful lumbosacral bone union.

Case 2. A 6-year-old male underwent vertical expandable prosthetic titanium rib (VEPTR) surgery with multiple rod extension procedures. Subsequently, at the age of 10 years, a combined two-stage anterior (L1-3) and posterior (T8-iliac) fixation with T9 hemivertebrectomy was performed. As a result of subsequent nonunion with screw loosening, additional rigid fixation at the pubic symphysis was performed 1 month after posterior fixation. Bone union was finally achieved 1 year after all the surgical interventions.

Conclusions

Rigid fixation at the pubic symphysis may play a significant role in achieving rigid bone union for unstable lumbopelvic connection, such as SA, Renshaw type III or IV.

Laparoscopic-Assisted Anorectal Pull-Through for Currarino Syndrome

Objective: Currarino syndrome (CS) is characterized by the triad of sacral anomalies, presacral tumor, and anorectal malformation (ARM). This study evaluates the feasibility and outcomes of laparoscopic-assisted anorectal pull-through (LAARP) for CS. Materials and Methods: Children admitted for primary or redo repair of CS through LAARP between 2016 and 2019 were reviewed. The indication of redo included constipation with megarectosigmoid, residual presacral mass, anastomosis leak, and secondary fistula. ARM was corrected by excision of rectal stenosis, fistula, and its associated megarectosigmoid. This was followed by a complete surgical resection of the presacral tumor, with subsequent pull-through and anocolic anastomosis. This was done with a combined laparoscopic and transanal approach. The detailed surgical techniques, early postoperative complications, and mid-term functional outcomes were summarized. Results: Fourteen patients underwent LAARP for primary (N = 4) and redo (N = 10) repair of CS. Four of them had colostomy previously. Mean age at operation was 20.7 ± 13.9 months. Mean operative time was 120 ± 25 minutes. Median hospital stay was 8 days (range 7-9 days) postoperatively. None of the patients developed early postoperative complications such as anastomotic leaks, presacral abscesses, recurrent fistulas, and residual mass. Bowel function was assessed 1 year after LAARP in 10 patients. Mean follow-up time was 15.9 months. The frequency of bowel movements was 3.3 ± 1.5/day. Constipation occurred in 2 patients. Occasional soiling (<3 times/week) was reported in 4 patients and frequent soiling (>3 times/week) was in 1. Conclusion: LAARP for CS is safe and effective.

Currarino syndrome presenting as a cerebrospinal fluid leak from the dermal sinus tract: case report

Currarino syndrome is an autosomal dominant condition with variable expressivity and penetrance that is associated with several classic features: sacral dysgenesis, presacral mass, and/or anorectal anomalies. The authors present a unique case in which the patient's initial presentation was a CSF leak from a sinus tract. The sinus tract was identified and disconnected from the thecal sac, obliterating the anterior sacral meningocele. This case represents a unique scenario in which Currarino syndrome manifested as a CSF leak from a dermal sinus tract.

The paleoepidemiology of Sacral Spina Bifida Occulta in population samples from the Dakhleh Oasis, Egypt

OBJECTIVE

To document sacral spina bifida occulta (SSB0) prevalence in a population sample from the Dakhleh Oasis, Egypt, and address methodological issues in recording and quantifying SSBO variations.

MATERIALS

442 adult sacra from two temporally disjunct samples from the same deme traversing the 3rd intermediate (TIP) and the Roman Periods.

METHODS

Sacra were scored for SSBO, excluding the sacral hiatus. Risk of SSBO was calculated with the common odds ratio and statistical significance by X². Data were compared to other archaeological SSBO data.

RESULTS

SSBO was present in 15.6% of the sample with a slight, but not significant, temporal increase (TIP to Roman Period) in males, and a significant age-correlated increase in both sexes. Most open sacra occurred in young adults.

CONCLUSIONS

Data support that SSBO can be considered as a morphogenetic variant. Dakhleh data fall within the prevalence range for most populations, however inter-population comparisons are complicated by methodological inconsistencies.

SIGNIFICANCE

SSBO can be used in paleogenetic research.

LIMITATIONS

Methodological differences in scoring SSBO prevent effective comparative study.

SUGGESTED FUTURE RESEARCH

Future studies require more rigorous and standardized scoring methods. aDNA may be used to corroborate the morphogenetic value of SSBO and determine its clinical significance.

From Biology to Genes and Back Again: Gene Discovery for Monogenic Forms of Beta-Cell Dysfunction in Diabetes

This review focuses on gene discovery strategies used to identify monogenic forms of diabetes caused by reduced pancreatic beta-cell number (due to destruction or defective development) or impaired beta-cell function. Gene discovery efforts in monogenic diabetes have identified 36 genes so far. These genetic causes have been identified using four main approaches: linkage analysis, candidate gene sequencing and most recently, exome and genome sequencing. The advent of next-generation sequencing has allowed researchers to move away from linkage analysis (relying on large pedigrees and/or multiple families with the same genetic condition) and candidate gene (relying on previous knowledge on the gene's role) strategies to use a gene agnostic approach, utilizing genetic evidence (such as variant frequency, predicted variant effect on protein function, and predicted mode of inheritance) to identify the causative mutation. This approach led to the identification of seven novel genetic causes of monogenic diabetes, six by exome sequencing and one by genome sequencing. In many of these cases, the disease-causing gene was not known to be important for beta-cell function prior to the gene discovery study. These novel findings highlight a new role for gene discovery studies in furthering our understanding of beta-cell function and dysfunction in diabetes. While many gene discovery studies in the past were led by knowledge in the field (through the candidate gene strategy), now they often lead the scientific advances in the field by identifying new important biological players to be further characterized by in vitro and in vivo studies.

Unbalanced Y;7 Translocation between Two Low-Similarity Sequences Leading to SRY-Positive 45,X Testicular Disorders of Sex Development

Unbalanced translocations of Y-chromosomal fragments harboring the sex-determining region Y gene (SRY) to the X chromosome or an autosome result in 46,XX and 45,X testicular disorders of sex development (DSD), respectively. Of these, Y;autosome translocation is an extremely rare condition. Here, we identified a 20-year-old man with a 45,X,t(Y;7)(q11.21;q35) karyotype, who exhibited unilateral cryptorchidism, small testis, intellectual disability, and various congenital anomalies. The fusion junction of the translocation was blunt, and the breakpoint-flanking regions shared only 50% similarity. These results indicate that Y;autosome translocations can occur between 2 low-similarity sequences, probably via nonhomologous end joining. Furthermore, translocations of a Ypterq11.21 fragment to 7q35 likely result in normal or only mildly impaired male-type sexual development, along with various clinical features of 7q deletion syndrome, although their effects on adult testicular function remain to be studied.

Expression, Clinical Significance, and Functional Prediction of MNX1 in Breast Cancer

Motor neuron and pancreas homeobox 1 (MNX1) is a key developmental gene. Previous studies found that it was upregulated in several tumors, but its role in breast cancer (BC) remains unclear. In order to have a better understanding of this gene in BC, we examined the expression of MNX1 in BC tissues and normal breast tissues by qRT-PCR and by analyzing data from The Cancer Genome Atlas (TCGA) database. We also assessed the association of MNX1 expression with BC clinicopathological features and investigated the impact of MNX1 on BC survival. Potential molecular function of MNX1 was predicted through protein-protein interactions and functional enrichment. The results showed that the expression of MNX1 was significantly increased in BC tissues, especially in the HER2-positive subtype, and MNX1 expression was associated with several clinical characteristics, including menopause status, receptor status, subtypes, tumor size, lymph node metastasis, and race. In addition, patients with higher MNX1 expression had poorer survival. Enrichment analysis suggested that MNX1 is probably involved in biological processes and pathways related to nuclear division, cell cycle, and p53 signaling. In conclusion, our study suggests that MNX1 may act as a tumor promoter in BC. We hope these findings will draw more attention to MNX1 in future cancer studies.

Spectrum of MNX1 Pathogenic Variants and Associated Clinical Features in Korean Patients with Currarino Syndrome

Background

The major genetic cause of Currarino syndrome (CS), a congenital malformation syndrome typically characterized by sacral agenesis, anorectal malformation, and presence of a pre-sacral mass, is known to be pathogenic variants in motor neuron and pancreas homeobox 1 (MNX1), which exist in almost all familial cases and 30% of sporadic cases. Less commonly, a large deletion or a complex rearrangement involving the 7q36 region is associated with CS. We investigated the spectrum of MNX1 pathogenic variants and associated clinical features in the Korean patients with CS.

Methods

We enrolled 25 patients with CS, including 24 sporadic cases and one familial case. Direct sequencing of MNX1 and multiplex ligation-dependent probe amplification were performed. We also analyzed clinical phenotypes and evaluated genotype-phenotype correlations.

Results

We identified six novel variants amongst a total of six null variants, one missense variant, and one large deletion. The null variants included four frameshift variants (p.Gly98Alafs^*124, p.Gly145Alafs^*77, p.Gly151Leufs^*67, and p.Ala216Profs^*5) and two nonsense variants (p.Tyr186^* and p.Gln212^*). The missense variant, p.Lys295Gln, was located in the highly-conserved homeobox domain and was predicted to be deleterious. A large deletion involving the 7q36 region was detected in one patient. Pathogenic variants in MNX1 were detected in 28% of all CS cases and 25% of sporadic cases. The clinical phenotype was variable in patients with and without pathogenic variants; no significant genotype-phenotype correlation was observed.

Conclusions

This study revealed the spectrum and phenotypic variability of MNX1 pathogenic variants in the Korean population.

MNX1 reduces sensitivity to anoikis by activating TrkB in human glioma cells

Glioma is the most common type of malignant intracranial tumor in adults and is associated with the highest mortality rate. Although surgery, radiotherapy, chemotherapy and other treatment methods have progressed, the median survival of patients with glioma is only 14–15 months. Glioma cells are able to penetrate along blood vessels and invade into the surrounding normal brain tissue so that an overall resection of the tumor cannot be performed. In the process of metastasis, the resistance of cancer cells to anoikis has an important role. When tumor cells escape from their original environment, anoikis resistance aids their survival. In the present study, reverse transcription-semi-quantitative polymerase chain reaction (RT-sqPCR), RT-quantitative PCR and western blotting demonstrated that the transcription factor, motor neuron and pancreas homeobox 1 (MNX1), was ectopically expressed in glioma cells compared with normal HUVEC-C human umbilical vein endothelial cells. Furthermore, its expression was higher in more malignant glioma cell lines (T98G and M059K) compared with the less malignant glioma cell line (U-87 MG) and normal HUVEC-C cells. An adhesion assay using fibronectin demonstrated that MNX1 and tyrosine kinase receptor B (TrkB) overexpression in HUVEC-C and U-87 MG cells reduced adhesion and forced them to suspend. Additionally, MNX1 and TrkB overexpression was demonstrated to increase the ability of cells to bypass anoikis. MNX1 and TrkB knockdown increased adhesion and promoted apoptosis after suspension. It was further demonstrated that MNX1 functioned as a transcription factor binding in the upstream regulatory region of TrkB to activate its expression. The results of the present study suggested that MNX1 may suppress the adhesion and apoptosis rates of tumor cells by activating TrkB. The results of the present study suggest that MNX1 may represent a novel therapeutic target for the treatment of gliomas.

WT1-Expressing Interneurons Regulate Left-Right Alternation during Mammalian Locomotor Activity

The basic pattern of activity underlying stepping in mammals is generated by a neural network located in the caudal spinal cord. Within this network, the specific circuitry coordinating left-right alternation has been shown to involve several groups of molecularly defined interneurons. Here we characterize a population of spinal neurons that express the Wilms' tumor 1 (WT1) gene and investigate their role during locomotor activity in mice of both sexes. We demonstrate that WT1-expressing cells are located in the ventromedial region of the spinal cord of mice and are also present in the human spinal cord. In the mouse, these cells are inhibitory, project axons to the contralateral spinal cord, terminate in close proximity to other commissural interneuron subtypes, and are essential for appropriate left-right alternation during locomotion. In addition to identifying WT1-expressing interneurons as a key component of the locomotor circuitry, this study provides insight into the manner in which several populations of molecularly defined interneurons are interconnected to generate coordinated motor activity on either side of the body during stepping.SIGNIFICANCE STATEMENT In this study, we characterize WT1-expressing spinal interneurons in mice and demonstrate that they are commissurally projecting and inhibitory. Silencing of this neuronal population during a locomotor task results in a complete breakdown of left-right alternation, whereas flexor-extensor alternation was not significantly affected. Axons of WT1 neurons are shown to terminate nearby commissural interneurons, which coordinate motoneuron activity during locomotion, and presumably regulate their activity. Finally, the WT1 gene is shown to be present in the spinal cord of humans, raising the possibility of functional homology between these species. This study not only identifies a key component of the locomotor circuitry but also begins to unravel the connectivity among the growing number of molecularly defined interneurons that comprise this neural network.

Multiple neurosurgical treatments for different members of the same family with Currarino syndrome

INTRODUCTION

Currarino's syndrome (CS) is an autosomal dominant disorder of embryonic development causing a rare malformating syndrome characterized by a triad of an anorectal malformations, presacral mass (most commonly an anterior sacral meningocele) and sacral bony defects. Mutations of the HLXB9 gene have been identified in most CS cases, but a precise genotype-phenotype correlation has not been described so far. Family screening is obligatory. The diagnosis is usually made during childhood and rarely in adulthood. In this context, imaging, and especially MRI plays a major role in the diagnosis of this syndrome. Surgical management is provided by pediatric surgeons or neurosurgeons.

FAMILIAL CASE REPORT

Here, we present a family case report with CS requiring different neurosurgical management. The son, a 3-year-old boy, developed a tethered spinal cord syndrome associated to a lipoma of the filum terminale, a sacro-coccygeal teratoma and an anal adhesion. A combined surgical approach permitted a good evolution on the urinary and digestive functions despite a persistent fecal incontinence. The 2-year-old daughter presented with a cyst of the thyreoglossal tract infected and fistulized to the skin. She was also followed for a very small lipoma of the filum terminale that required a neurosurgical approach. The father, 44-year-old, manifested functional digestive and urinary disorders caused by a giant anterior sacral meningocele. The ligation of the neck of the cyst and aspiration of the liquid inside in full through a posterior partial approach permit a complete collapse of the cyst with an instantly satisfactory clinical outcome.

CONCLUSION

In these cases, cooperation between pediatric surgeons and neurosurgeons was crucial. The follow-up of these patients should be done in a spina bifida clinic. A geneticist evaluation must be offered to the patient in the case of a CS as well as a clinical evaluation of the relatives (parents, siblings).

A review of genetic factors contributing to the etiopathogenesis of anorectal malformations

BACKGROUND

Anorectal malformation (ARM) is a common congenital anomaly with a wide clinical spectrum. Recently, many genetic and molecular studies have been conducted worldwide highlighting the contribution of genetic factors in its etiology. We summarize the current literature on such genetic factors.

MATERIALS AND METHODS

Literature search was done using different combinations of terms related to genetics in anorectal malformations. From 2012 to June 2017, articles published in the English literature and studies conducted on human population were included.

OBSERVATIONS AND RESULTS

A paradigm shift was observed from the earlier studies concentrating on genetic aberrations in specific pathways to genome wide arrays exploring single nucleotide polymorphisms (SNPs) and copy number variations (CNVs) in ARM patients. Rare CNVs (including 79 genes) and SNPs have been found to genetically contribute to ARM. Out of disrupted 79 genes one such putative gene is DKK4. Down regulation of CDX-1 gene has also been implicated in isolated ARM patients. In syndromic ARM de novo microdeletion at 17q12 and a few others have been identified.

CONCLUSION

Major genetic aberrations proposed in the pathogenesis of ARM affect members of the Wnt, Hox (homebox) genes, Sonic hedgehog (Shh) and Gli2, Bmp4, Fgf and CDX1 signalling pathways; probable targets of future molecular gene therapy.

Anterior sacral meningocele infected with Fusobacterium in a patient with recently diagnosed colorectal carcinoma - a case report

Background

Anterior sacral meningoceles are rare, and usually occur with other malformations of the posterior lower spine. While these are more frequently reported in pediatric cohorts, we report a case in an elderly woman.

Case presentation

We report on a 71 year-old woman with a recently diagnosed colorectal adenocarcinoma who presented with a severe bacterial meningitis. The cerebrospinal fluid cell count revealed a pleocytosis of 80,000 cells/μl and a severe disturbance of the blood-brain-barrier. Fusobacterium nucleatum was cultured as the causing pathogen. A lumbar MRI showed, in addition to contrast-enhancing meninges as sign of inflammation, a presacral mass. In the next step, the mass was diagnosed as an anterior sacral meningocele connected to the gut. An adequate antibiotic was used to treat the leptomeningitis. The connection between gut and meningocele was closed surgically and the patient recovered well and underwent further treatment of her colorectal adenocarcinoma.

Conclusion

We report on a case of meningitis with an anterior sacral meningocele that was connected to the gut in a patient with a infiltrative colorectal adenocarcinoma. Anatomic variants have to be considered as rare causes of meningitis with typical intestinal germs.

Currarino syndrome: does the presence of a genetic anomaly correlate with a more severe phenotype? A multicentre study

BACKGROUND/PURPOSE

Currarino syndrome (CS) phenotype, initially described as the triad of hemisacrum, anorectal malformation (ARM) and presacral mass, can be extremely variable. The triad is often incomplete and 3 main CS phenotypical subtypes have been described: Complete, Mild and Minimal. Various associated malformations are often present. Mutations in the MNX1 gene are the main genetic background of CS, although they are not present in almost half of the cases. Aim of our study is to analyze the distribution of the 3 CS subtypes and the incidence of associated malformations in a large sample of patients and to add information about the role of the genetic testing in guiding the diagnostic and prognostic evaluation of CS patients.

METHODS

A multicentre retrospective data collection was performed. CS patients' phenotype was accurately analyzed according to a diagnostic-therapeutic standardized data collection sheet. The distribution of the three CS types and the frequency of each associated malformation were calculated. The phenotype of the patients with a known genetic anomaly was compared to the phenotype of the population with no genetic diagnosis, in order to determine whether the presence of a known genetic defect could correlate with a more severe CS phenotype.

RESULTS

Data from 45 patients were analyzed. Twenty patients (44.5%) presented a Complete CS type, 19 (42.2%) a Mild CS and 6 (13.3%) a Minimal CS. In addition to the classical triad elements, 38 (84.5%) patients showed associated anomalies. The group of patients who resulted positive for a MNX1 mutation comprised a higher number (56.5%) of Complete CS cases than the group of patients that did not carry any MNX1 mutation (13%) (p = 0.0085). We could not find any relationship between CS subtype and the number of associated anomalies (p = 0.5102).

CONCLUSIONS

The presence of a MNX1 mutation seems to correlate with a more severe CS phenotype. MNX1 seems the main responsible for the expression and the severity of the CS triad, while the associated anomalies appear to be prevalently determined by genes sited on different loci. A thorough multidisciplinary diagnostic overview of CS patients should always include genetic counseling and analysis, both in postnatal and prenatal settings.

TYPE OF STUDY

Retrospective Study.

LEVEL OF EVIDENCE

II.

Deregulation of ZPR1 causes respiratory failure in spinal muscular atrophy

Spinal muscular atrophy (SMA) is caused by the low levels of survival motor neuron (SMN) protein and is characterized by motor neuron degeneration and muscle atrophy. Respiratory failure causes death in SMA but the underlying molecular mechanism is unknown. The zinc finger protein ZPR1 interacts with SMN. ZPR1 is down regulated in SMA patients. We report that ZPR1 functions downstream of SMN to regulate HoxA5 levels in phrenic motor neurons that control respiration. Spatiotemporal inactivation of Zpr1 gene in motor neurons down-regulates HoxA5 and causes defects in the function of phrenic motor neurons that results in respiratory failure and perinatal lethality in mice. Modulation in ZPR1 levels directly correlates and influences levels of HoxA5 transcription. In SMA mice, SMN-deficiency causes down-regulation of ZPR1 and HoxA5 that result in degeneration of phrenic motor neurons. Identification of ZPR1 and HoxA5 as potential targets provides a paradigm for developing strategies to treat respiratory distress in SMA.

Subtelomeric rearrangements in Indian children with idiopathic intellectual disability/developmental delay: Frequency estimation & clinical correlation using fluorescence in situ hybridization (FISH)

Background & objectives:

Subtelomeres are prone to deleterious rearrangements owing to their proximity to unique sequences on the one end and telomeric repetitive sequences, which increase their tendency to recombine, on the other end. These subtelomeric rearrangements resulting in segmental aneusomy are reported to contribute to the aetiology of idiopathic intellectual disability/developmental delay (ID/DD). We undertook this study to estimate the frequency of subtelomeric rearrangements in children with ID/DD.

Methods:

One hundred and twenty seven children with idiopathic ID/DD were tested for subtelomeric rearrangements using karyotyping and FISH. Blood samples were cultured, harvested, fixed and GTG-banded using the standard protocols.

Results:

Rearrangements involving the subtelomeres were observed in 7.8 per cent of the tested samples. Detection of rearrangements visible at the resolution of the karyotype constituted 2.3 per cent, while those rearrangements detected only with FISH constituted 5.5 per cent. Five deletions and five unbalanced translocations were detected. Analysis of parental samples wherever possible was informative regarding the inheritance of the rearrangement.

Interpretation & conclusions:

The frequency of subtelomeric rearrangements observed in this study was within the reported range of 0-35 per cent. All abnormal genotypes were clinically correlated. Further analysis with array technologies presents a future prospect. Our results suggest the need to test individuals with ID/DD for subtelomeric rearrangements using sensitive methods such as FISH.

Growth Hormone (GH) and Rehabilitation Promoted Distal Innervation in a Child Affected by Caudal Regression Syndrome

Caudal regression syndrome (CRS) is a malformation occurring during the fetal period and mainly characterized by an incomplete development of the spinal cord (SC), which is often accompanied by other developmental anomalies. We studied a 9-month old child with CRS who presented interruption of the SC at the L2–L3 level, sacral agenesis, a lack of innervation of the inferior limbs (flaccid paraplegia), and neurogenic bladder and bowel. Given the known positive effects of growth hormone (GH) on neural stem cells (NSCs), we treated him with GH and rehabilitation, trying to induce recovery from the aforementioned sequelae. The Gross Motor Function Test (GMFM)-88 test score was 12.31%. After a blood analysis, GH treatment (0.3 mg/day, 5 days/week, during 3 months and then 15 days without GH) and rehabilitation commenced. This protocol was followed for 5 years, the last GH dose being 1 mg/day. Blood analysis and physical exams were performed every 3 months initially and then every 6 months. Six months after commencing the treatment the GMFM-88 score increased to 39.48%. Responses to sensitive stimuli appeared in most of the territories explored; 18 months later sensitive innervation was complete and the patient moved all muscles over the knees and controlled his sphincters. Three years later he began to walk with crutches, there was plantar flexion, and the GMFM-88 score was 78.48%. In summary, GH plus rehabilitation may be useful for innervating distal areas below the level of the incomplete spinal cord in CRS. It is likely that GH acted on the ependymal SC NSCs, as the hormone does in the neurogenic niches of the brain, and rehabilitation helped to achieve practically full functionality.

Sacral agenesis: a pilot whole exome sequencing and copy number study

Background

Caudal regression syndrome (CRS) or sacral agenesis is a rare congenital disorder characterized by a constellation of congenital caudal anomalies affecting the caudal spine and spinal cord, the hindgut, the urogenital system, and the lower limbs. CRS is a complex condition, attributed to an abnormal development of the caudal mesoderm, likely caused by the effect of interacting genetic and environmental factors. A well-known risk factor is maternal type 1 diabetes.

Method

Whole exome sequencing and copy number variation (CNV) analyses were conducted on 4 Caucasian trios to identify de novo and inherited rare mutations.

Results

In this pilot study, exome sequencing and copy number variation (CNV) analyses implicate a number of candidate genes, including SPTBN5, MORN1, ZNF330, CLTCL1 and PDZD2. De novo mutations were found in SPTBN5, MORN1 and ZNF330 and inherited predicted damaging mutations in PDZD2 (homozygous) and CLTCL1 (compound heterozygous). Importantly, predicted damaging mutations in PTEN (heterozygous), in its direct regulator GLTSCR2 (compound heterozygous) and in VANGL1 (heterozygous) were identified. These genes had previously been linked with the CRS phenotype.

Two CNV deletions, one de novo (chr3q13.13) and one homozygous (chr8p23.2), were detected in one of our CRS patients. These deletions overlapped with CNVs previously reported in patients with similar phenotype.

Conclusion

Despite the genetic diversity and the complexity of the phenotype, this pilot study identified genetic features common across CRS patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-016-0359-2) contains supplementary material, which is available to authorized users.

Polycomb Repressive Complex 2 Enacts Wnt Signaling in Intestinal Homeostasis and Contributes to the Instigation of Stemness in Diseases Entailing Epithelial Hyperplasia or Neoplasia

Canonical Wnt/β-catenin signaling regulates the homeostasis of intestinal epithelium by controlling the balance between intestinal stem cell self-renewal and differentiation but epigenetic mechanisms enacting the process are not known. We hypothesized that epigenetic regulator, Polycomb Repressive Complex-2 (PRC2), is involved in Wnt-mediated epithelial homeostasis on the crypt-villus axis and aberrancies therein are implicated both in celiac disease and in intestinal malignancies. We found that PRC2 establishes repressive crypt and villus specific trimethylation of histone H3 lysine 27 (H3K27me3) signature on genes responsible for, for example, nutrient transport and cell killing in crypts and, for example, proliferation and differentiation in mature villi, suggesting that PRC2 facilitates the Wnt-governed intestinal homeostasis. When celiac patients are on gluten-containing diet PRC2 is out-of-bounds active and consequently its target genes were found affected in intestinal epithelium. Significant set of effective intestinal PRC2 targets are also differentially expressed in colorectal adenoma and carcinomas. Our results suggest that PRC2 gives rise and maintains polar crypt and villus specific H3K27me3 signatures. As H3K27me3 is a mark enriched in developmentally important genes, identified intestinal PRC2 targets are possibly imperative drivers for enterocyte differentiation and intestinal stem cell maintenance downstream to Wnt-signaling. Our work also elucidates the mechanism sustaining the crypt hyperplasia in celiac disease and suggest that PRC2-dependent fostering of epithelial stemness is a common attribute in intestinal diseases in which epithelial hyperplasia or neoplasia prevails. Finally, this work demonstrates that in intestine PRC2 represses genes having both pro-stemness and pro-differentiation functions, fact need to be considered when designing epigenetic therapies including PRC2 as a drug target. Stem Cells 2017;35:445-457.

Fatal Meningitis in a 14-Month-Old with Currarino Triad

We report a case of a 14-month-old girl with undiagnosed Currarino triad presenting acutely with meningitis caused by enteric commensals. Head CT demonstrated a large pneumocephalus. A fistulous neurenteric tract through a presacral mass was present on spine MRI and abdominal CT. The patient had a history of constipation for the last three months. However, an underlying diagnosis of Currarino triad had not been suspected. In retrospect, a sickle-shaped sacral anomaly was present on a previous abdominal radiograph. The patient succumbed to complications of meningitis. The purpose of the case report is to highlight the potentially fatal complication of Currarino triad and sensitize radiologists to look actively for sacral anomalies on abdominal radiographs, especially of children with chronic constipation.

Sacral agenesis and neurogenic bladder: Long-term outcomes of bladder and kidney function

BACKGROUND

Sacral agenesis (SA) is a rare congenital condition that refers to the absence of part or all of two or more lower sacral vertebral bodies. It can be associated with neurogenic bladder dysfunction that does not necessarily correlate with the level of spinal or skeletal defect. Patients with SA should undergo urodynamic studies (UDS) to guide lower urinary tract (LUT) management.

OBJECTIVE

This review aimed to update the present institutional experience since 1981 of this rare patient population with detailed, long-term follow-up of bladder and kidney function.

STUDY DESIGN

A single institution, retrospective, IRB-approved review was performed on patients born after January 1, 1981 with an isolated diagnosis of sacral agenesis without spina bifida, and followed with urologic involvement at Boston Children's Hospital. Records were reviewed for demographics, radiologic imaging, UDS including cystometrogram (CMG) and electromyography (EMG), surgery, and blood chemistries. Comparisons were made between groups of patients based on age at diagnosis, with specific focus on renal function and stability of neurogenic bladder lesion.

RESULTS

Forty-three patients were identified: 23 female and 20 male. Thirty-seven children (86%) had a known age of diagnosis. Nineteen were diagnosed before 2 months old, including five who were diagnosed prenatally, 11 were diagnosed between 2 and 18 months, and seven were diagnosed after 18 months. All 43 had UDS, with 24 (55.8%) studied at the time of diagnosis (Summary Table). Twenty had serial full UDS, with 30% demonstrating neurourologic instability. None developed end-stage renal disease (ESRD) or required spinal cord detethering.

DISCUSSION

Many children with SA appeared to be diagnosed prenatally or early in life; SA was mostly identified during evaluation of associated anomalies. Though UDS aid in urologic management, testing was not routinely utilized at the time of diagnosis.

CONCLUSIONS

This review of long-term follow-up in SA patients showed stable LUT and renal function, with minimal risk of progression to ESRD.

Currarino triad with Müllerian duct anomaly in mother and daughter without MNX1 gene mutation

The Currarino triad is a unique complex of congenital caudal anomalies, including anorectal malformation, sacral bony defect and presacral mass. This triad may be associated with Müllerian duct anomalies, such as duplication of the vagina and uterus. Each of these diseases has a familial tendency and sometimes coexist within families. But, when coexisting in familial cases, nearly all reported cases revealed mutations of the motor neuron and pancreas homeobox 1 (MNX1) gene. Familial cases of Currarino triad combined with Müllerian duct anomaly without MNX1 gene mutation are very rare. Here we report cases of mother and daughter, who had Currarino triad and Müllerian duct anomaly without MNX1 gene mutation, along with a brief literature review.

Pronephric tubule morphogenesis in zebrafish depends on Mnx mediated repression of irx1b within the intermediate mesoderm

Mutations in the homeobox transcription factor MNX1 are the major cause of dominantly inherited sacral agenesis. Studies in model organisms revealed conserved mnx gene requirements in neuronal and pancreatic development while Mnx activities that could explain the caudal mesoderm specific agenesis phenotype remain elusive. Here we use the zebrafish pronephros as a simple yet genetically conserved model for kidney formation to uncover a novel role of Mnx factors in nephron morphogenesis. Pronephros formation can formally be divided in four stages, the specification of nephric mesoderm from the intermediate mesoderm (IM), growth and epithelialisation, segmentation and formation of the glomerular capillary tuft. Two of the three mnx genes in zebrafish are dynamically transcribed in caudal IM in a time window that proceeds segmentation. We show that expression of one mnx gene, mnx2b, is restricted to the pronephric lineage and that mnx2b knock-down causes proximal pronephric tubule dilation and impaired pronephric excretion. Using expression profiling of embryos transgenic for conditional activation and repression of Mnx regulated genes, we further identified irx1b as a direct target of Mnx factors. Consistent with a repression of irx1b by Mnx factors, the transcripts of irx1b and mnx genes are found in mutual exclusive regions in the IM, and blocking of Mnx functions results in a caudal expansion of the IM-specific irx1b expression. Finally, we find that knock-down of irx1b is sufficient to rescue proximal pronephric tubule dilation and impaired nephron function in mnx-morpholino injected embryos. Our data revealed a first caudal mesoderm specific requirement of Mnx factors in a non-human system and they demonstrate that Mnx-dependent restriction of IM-specific irx1b activation is required for the morphogenesis and function of the zebrafish pronephros.