Microtubular TRIM36 E3 Ubiquitin Ligase in Embryonic Development and Spermatogenesis

TRIM36 is a member of the tripartite motif (TRIM) family of RING-containing proteins, also known as Haprin, which was first discovered for its abundance in testis and found to be implicated in the spermatozoa acrosome reaction. TRIM36 is a microtubule-associated E3 ubiquitin ligase that plays a role in cytoskeletal organization, and according to data gathered in different species, coordinates growth speed and stability, acting on the microtubules’ plus end, and impacting on cell cycle progression. TRIM36 is also crucial for early developmental processes, in Xenopus, where it is needed for dorso-ventral axis formation, but also in humans as bi-allelic mutations in the TRIM36 gene cause a form of severe neural tube closure defect, called anencephaly. Here, we review TRIM36-related mechanisms implicated in such composite physiological and pathological processes.

Nuclear factor I-C disrupts cellular homeostasis between autophagy and apoptosis via miR-200b-Ambra1 in neural tube defects

Impaired autophagy and excessive apoptosis disrupt cellular homeostasis and contribute to neural tube defects (NTDs), which are a group of fatal and disabling birth defects caused by the failure of neural tube closure during early embryonic development. However, the regulatory mechanisms underlying NTDs and outcomes remain elusive. Here, we report the role of the transcription factor nuclear factor I-C (NFIC) in maintaining cellular homeostasis in NTDs. We demonstrated that abnormally elevated levels of NFIC in a mouse model of NTDs can interact with the miR-200b promoter, leading to the activation of the transcription of miR-200b, which plays a critical role in NTD formation, as reported in our previous study. Furthermore, miR-200b represses autophagy and triggers apoptosis by directly targeting the autophagy-related gene Ambra1 (Autophagy/Beclin1 regulator 1). Notably, miR-200b inhibitors mitigate the unexpected effects of NFIC on autophagy and apoptosis. Collectively, these results indicate that the NFIC-miR-200b-Ambra1 axis, which integrates transcription- and epigenome-regulated miRNAs and an autophagy regulator, disrupts cellular homeostasis during the closure of the neural tube, and may provide new insight into NTD pathogenesis.

Disruption of Folate Metabolism Causes Poor Alignment and Spacing of Mouse Conceptuses for Multiple Generations

Abnormal uptake or metabolism of folate increases risk of human pregnancy complications, though the mechanism is unclear. Here, we explore how defective folate metabolism influences early development by analysing mice with the hypomorphic Mtrrgt mutation. MTRR is necessary for methyl group utilisation from folate metabolism, and the Mtrrgt allele disrupts this process. We show that the spectrum of phenotypes previously observed in Mtrrgt/gt conceptuses at embryonic day (E) 10.5 is apparent from E8.5 including developmental delay, congenital malformations, and placental phenotypes. Notably, we report misalignment of some Mtrrgt conceptuses within their implantation sites from E6.5. The degree of misorientation occurs across a continuum, with the most severe form visible upon gross dissection. Additionally, some Mtrrgt/gt conceptuses display twinning. Therefore, we implicate folate metabolism in blastocyst orientation and spacing at implantation. Skewed growth likely influences embryo development since developmental delay and heart malformations (but not defects in neural tube closure or trophoblast differentiation) associate with severe misalignment of Mtrrgt/gt conceptuses. Typically, the uterus is thought to guide conceptus orientation. To investigate a uterine effect of the Mtrrgt allele, we manipulate the maternal Mtrr genotype. Misaligned conceptuses were observed in litters of Mtrr+/+, Mtrr+/gt, and Mtrrgt/gt mothers. While progesterone and/or BMP2 signalling might be disrupted, normal decidual morphology, patterning, and blood perfusion are evident at E6.5 regardless of conceptus orientation. These observations argue against a post-implantation uterine defect as a cause of conceptus misalignment. Since litters of Mtrr+/+ mothers display conceptus misalignment, a grandparental effect is explored. Multigenerational phenotype inheritance is characteristic of the Mtrrgt model, though the mechanism remains unclear. Genetic pedigree analysis reveals that severe conceptus skewing associates with the Mtrr genotype of either maternal grandparent. Moreover, the presence of conceptus skewing after embryo transfer into a control uterus indicates that misalignment is independent of the peri- and/or post-implantation uterus and instead is likely attributed to an embryonic mechanism that is epigenetically inherited. Overall, our data indicates that abnormal folate metabolism influences conceptus orientation over multiple generations with implications for subsequent development. This study casts light on the complex role of folate metabolism during development beyond a direct maternal effect.

Emergence of planar cell polarity from the interplay of asymmetric interaction and tissue-level gradients

Planar cell polarity (PCP) - asymmetric localization of proteins at cell-cell interface - is essential for embryonic development and physiological functions. Abnormalities in PCP can lead to neural tube closure defects, misalignment in hair follicles etc. Thus, decoding the mechanism responsible for PCP establishment and maintenance remains an open fundamental question. While various molecules-broadly classified into 'global' and 'local' modules have been well investigated; their necessity and sufficiency in explaining PCP and connecting their perturbations and defects in experimentally observed patterns has not been examined. Here, we develop a minimal model that captures the proposed features of these two modules- a tissue level gradient (global) and asymmetric localization of protein complexes (local). Our model results suggest that while polarity can emerge in absence of a gradient; the gradient can provide the direction of polarity as well as offer robustness for maintenance of PCP in presence of stochastic perturbations. We also recapitulated swirling patterns (seen experimentally) and the features of non-domineering autonomy; using only three free parameters in the model - protein binding rate; concentration of proteins forming heterodimer across cell boundaries and steepness of gradient. Our results explain how self-stabilizing asymmetric localisations in presence of tissue-level gradient can lead to robust PCP patterns in diverse biological systems and reveals the minimal design principles for a polarized system.

Eph and Ephrin Variants in Malaysian Neural Tube Defect Families

Neural tube defects (NTDs) are among the most common of birth defects. Despite the many gene candidates identified in certain population; none have thus far been regarded as compelling enough as a candidate for different populations. As candidate genes for NTDs, this study focussed on Ephs and ephrins owing to growing evidence for the role of this gene family during neural tube closure in mouse models. Eph and ephrin genes were analysed in 31 Malaysian individuals comprising 7 individuals with sporadic spina bifida, 14 parents and siblings and 10 unrelated controls. Whole exome sequencing analysis was performed to identify variants in 22 known EphAs, EphBs, ephrinAs and ephrinBs genes. All candidate variants in Eph-ephrin genes were subjected to bioinformatics analysis to determine possible pathogenicity. We reported 3 out of 7 spina bifida probands and 3 out of 13 parents and 1 twin-sibling, carried a variant in either EPHA2 (rs147977279), EPHB6 (rs780569137) or EFNB1 (rs772228172). Analysis of public databases like 1000 Genome phase 3, GnomAD, ExAC, ESP, TOPMED and SGVP shows that these variants are rare, and they were not present in any of the unrelated controls. In exome datasets of the probands and parent of the probands with Eph and ephrin variants, the genotypes of spina bifida-related genes were compared to investigate the probability of the gene-gene interaction in relation to environmental risk factors. In summary, we report the presence of Eph and ephrin gene variants that are prevalent in a small cohort of spina bifida patients in Malaysian families.

When Bigger Is Better: 3D RNA Profiling of the Developing Head in the Catshark Scyliorhinus canicula

We report the adaptation of RNA tomography, a technique allowing spatially resolved, genome-wide expression profiling, to a species occupying a key phylogenetic position in gnathostomes, the catshark Scyliorhinus canicula. We focused analysis on head explants at an embryonic stage, shortly following neural tube closure and of interest for a number of developmental processes, including early brain patterning, placode specification or the establishment of epithalamic asymmetry. As described in the zebrafish, we have sequenced RNAs extracted from serial sections along transverse, horizontal and sagittal planes, mapped the data onto a gene reference taking advantage of the high continuity genome recently released in the catshark, and projected read counts onto a digital model of the head obtained by confocal microscopy. This results in the generation of a genome-wide 3D atlas, containing expression data for most protein-coding genes in a digital model of the embryonic head. The digital profiles obtained for candidate forebrain regional markers along antero-posterior, dorso-ventral and left-right axes reproduce those obtained by in situ hybridization (ISH), with expected relative organizations. We also use spatial autocorrelation and correlation as measures to analyze these data and show that they provide adequate statistical tools to extract novel expression information from the model. These data and tools allow exhaustive searches of genes exhibiting any predefined expression characteristic, such a restriction to a territory of interest, thus providing a reference for comparative analyses across gnathostomes. This methodology appears best suited to species endowed with large embryo or organ sizes and opens novel perspectives to a wide range of evo-devo model organisms, traditionally counter-selected on size criterion.

Closure of large lumbosacral defect using a combined method of bilateral bipedicle flap with lateral releasing incision and Integra® dermal regeneration template

BACKGROUND: Myelomeningocele is one of the most complex congenital malformations of the central nervous system. It is one of the most common types of spina bifida which involves a failure of neural tube closure. Reconstruction surgery for myelomeningocele had always been challenging for plastic and neurosurgeons. CLINICAL CASE: We report a case of a new-born with lumbosacral myelomeningocele who received treatment in the Hospital Universiti Sains Malaysia. The myelomeningocele was repaired by the neurosurgery team and subsequently, the child was left with huge lumbosacral skin defect. The large defect was successfully covered by using a combined method of bilateral bipedicle flap with lateral releasing incision and remaining lumbosacral and secondary defect resurfaced using Integra dermal regeneration template (DRT). We used ACTICOAT interfaced negative pressure wound therapy (NPWT) as our main dressing in preparing the wound bed for autologous epidermal graft. The result of our closure technique provides tension free closure. DISCUSSION: We incorporated bilateral bipedicle fasciocutaneous flap technique together with DRT for closure of the lumbosacral defect. The bilateral bipedicle flap with lateral releasing incision served to reduce tension on the skin at bilateral lumbar region. The DRT downsized the lumbosacral defect and NPWT dressing provided an optimal sterile environment in giving time for neodermis generation. The remaining secondary defect were also resurfaced utilizing DRT and autologous skin grafting. CONCLUSIONS: The outcome of surgery demonstrated that the combined use of bilateral bipedicle fasciocutaneous flap with lateral releasing incision and DRT with delayed skin grafting is safe, effective and provide long term stable and supple scar for large, exposed dura defect.

Diagnóstico prenatal de iniencefalia. Reporte de caso.

Iniencephaly is an infrequent and fatal neural tube defect that affects the occiput and neck, this occurs together with the widening of the foramen magnum, rachischisis and marked retro-flexion of the head. This entity belongs to the group of defects of neural tube closure. About 200 reports have been published in the literature. A diagnosis can be made using an ultrasound morphology test that is easy to perform due to the characteristic findings of the condition. Associated anomalies of the nervous system and other systems are frequently present during the ultrasound evaluation. Prenatal diagnosis of a neural tube defect that involves occipital defects and spinal and thoracic spine rachischisis accompanied by retro-flexion of the head should raise the diagnostic suspicion of iniencephaly. The prognosis is particularly bad with only a few cases of survival. Keywords: Iniencefalia, Neural tube defect, Prenatal diagnosis.

Microsurgical Resection of a Petroclival Epidermoid Cyst Using an Anterior Petrosectomy Approach: 2-Dimensional Operative Video

Epidermoid cysts are rare, benign lesions that result from inclusion of ectodermal elements during neural tube closure.1 Cysts are composed of desquamated epithelial cells and restrict diffusion on magnetic resonance imaging (MRI).2,3 Symptoms are attributable to anatomic location.4,5 In this video, we illustrate the surgical treatment of an epidermoid cyst located in the right cerebellopontine angle, petrous apex, and Meckel's cave. The patient, a 33-yr-old female with right-sided V1 trigeminal hypoesthesia, underwent surveillance imaging for 2 yr. However, she developed progressive V1 and V2 trigeminal hypoesthesia and imaging revealed enlargement of the lesion. Therefore, surgical resection was pursued. The patient consented to the procedure. The patient underwent a right middle fossa craniotomy and anterior petrosectomy. After identifying the greater superficial petrosal nerve and cutting the middle meningeal artery as it exited foramen spinosum, Kawase's triangle was drilled, and the dura over Meckel's cave and the subtemporal dura were opened. The lesion was resected, taking care to preserve the trigeminal nerve and the basilar artery. A retrosigmoid craniotomy was then fashioned. The cyst and its capsule were dissected off the brainstem and cranial nerves utilizing natural corridors between the trigeminal and vestibulocochlear nerves as well as between the facial and lower cranial nerves. Gross total resection was confirmed on postoperative MRI, and she was discharged home on postoperative day 5. Three months after surgery, she underwent formal pinprick testing, which revealed 95% loss of sensation in V1, 20% loss in V2, and normal sensation in V3. Three-month postoperative MRI showed no residual tumor.