Week Of Human Development Research Articles

Deciphering the impact of PROM1 alternative splicing on human photoreceptor development and maturation

Alternative splicing (AS) is a crucial mechanism contributing to proteomic diversity, which is highly regulated in tissue- and development-specific patterns. Retinal tissue exhibits one of the highest levels of AS. In particular, photoreceptors have a distinctive AS pattern involving the inclusion of microexons not found in other cell types. PROM1 whose encoded protein Prominin-1 is located in photoreceptor outer segments (OSs), undergoes exon 4 inclusion from the 12th post-conception week of human development through adulthood. Exon 4 skipping in PROM1 is associated with late-onset mild maculopathy, however its role in photoreceptor maturation and function is unknown. In this study retinal organoids, a valuable model system, were employed in combination with phosphorodiamidate morpholino oligos (PMOs) to assess the role of exon 4 AS in the development of human retina. Retinal organoids were treated with the PMOs for four weeks after which RT-PCR, western blotting and immunofluorescence analysis were performed to assess exon 4 exclusion and its impact on photoreceptors. The transcriptome of treated ROs was studied by bulk RNA-Seq. Our data demonstrate that 55% skipping of PROM1 exon 4 resulted in decreased Prominin-1 expression by 40%, abnormal accumulation of cones in the basal side of the retinal organoids as well as detectable cone photoreceptor cilium defects. Transcriptomic and western blot analyses revealed decreased expression of cone, inner segment and connecting cilium basal body markers, increased expression of genes associated with stress response and the ubiquitin-proteasome system, and downregulation of autophagy. Importantly, the use of retinal organoids provides a valuable platform to study AS and unravel disease mechanisms in a more physiologically relevant context, opening avenues for further research and potential therapeutic interventions. Together our data indicate that cones may be more sensitive to PROM1 exon 4 skipping and/or reduced Prominin-1 expression, corroborating the pathogenesis of late-onset mild maculopathy.

Single-cell analyses reveal transient retinal progenitor cells in the ciliary margin of developing human retina

The emergence of retinal progenitor cells and differentiation to various retinal cell types represent fundamental processes during retinal development. Herein, we provide a comprehensive single cell characterisation of transcriptional and chromatin accessibility changes that underline retinal progenitor cell specification and differentiation over the course of human retinal development up to midgestation. Our lineage trajectory data demonstrate the presence of early retinal progenitors, which transit to late, and further to transient neurogenic progenitors, that give rise to all the retinal neurons. Combining single cell RNA-Seq with spatial transcriptomics of early eye samples, we demonstrate the transient presence of early retinal progenitors in the ciliary margin zone with decreasing occurrence from 8 post-conception week of human development. In retinal progenitor cells, we identified a significant enrichment for transcriptional enhanced associate domain transcription factor binding motifs, which when inhibited led to loss of cycling progenitors and retinal identity in pluripotent stem cell derived organoids.

The emergence of human gastrulation upon in vitro attachment

While studied extensively in model systems, human gastrulation remains obscure. The scarcity of fetal biological material as well as ethical considerations limit our understanding of this process. Invitro attachment of natural blastocysts shed light on aspects of the second week of human development in the absence of the morphological manifestation of gastrulation. Stem cell-derived blastocyst models, blastoids, provide the opportunity to reconstitute pre- to post-implantation development invitro. Here we show that upon invitro attachment, human blastoids self-organize a BRA+ population and undergo gastrulation. Single-cell RNA sequencing of these models replicates the transcriptomic signature of the human gastrula. Analysis of developmental timing reveals that in both blastoid models and natural human embryos, the onset of gastrulation as defined by molecular markers, can be traced to timescales equivalent to 12days post fertilization. In all, natural human embryos and blastoid models self-organize primitive streak and mesoderm derivatives upon invitro attachment.

The Interplay of Cx26, Cx32, Cx37, Cx40, Cx43, Cx45, and Panx1 in Inner-Ear Development of Yotari (dab1-/-) Mice and Humans.

We investigated DAB1-protein deficiency in the inner-ear development of yotari in comparison to humans and wild-type (wt) mice by immunofluorescence for the expression of connexins (Cxs) and the pannexin Panx1. The spatial and temporal dynamics of Cx26, Cx32, Cx37, Cx40, Cx43, Cx45, and Panx1 were determined in the sixth and eighth weeks of human development and at the corresponding mouse embryonic E13.5 and E15.5, in order to examine gap junction intercellular communication (GJIC) and hemichannel formation. The quantification of the area percentage covered by positive signal was performed for the epithelium and mesenchyme of the cochlear and semicircular ducts and is expressed as the mean ± SD. The data were analysed by one-way ANOVA. Almost all of the examined Cxs were significantly decreased in the cochlear and semicircular ducts of yotari compared to wt and humans, except for Cx32, which was significantly higher in yotari. Cx40 dominated in human inner-ear development, while yotari and wt had decreased expression. The Panx1 expression in yotari was significantly lower than that in the wt and human inner ear, except at E13.5 in the mesenchyme of the wt and epithelium and mesenchyme of humans. Our results emphasize the relevance of GJIC during the development of vestibular and cochlear functions, where they can serve as potential therapeutic targets in inner-ear impairments.

Huntingtin CAG expansion impairs germ layer patterning in synthetic human 2D gastruloids through polarity defects.

ABSTRACTHuntington's disease (HD) is a fatal neurodegenerative disorder caused by an expansion of the CAG repeats in the huntingtin gene (HTT). Although HD has been shown to have a developmental component, how early during human embryogenesis the HTT-CAG expansion can cause embryonic defects remains unknown. Here, we demonstrate a specific and highly reproducible CAG length-dependent phenotypic signature in a synthetic model for human gastrulation derived from human embryonic stem cells (hESCs). Specifically, we observed a reduction in the extension of the ectodermal compartment that is associated with enhanced activin signaling. Surprisingly, rather than a cell-autonomous effect, tracking the dynamics of TGFβ signaling demonstrated that HTT-CAG expansion perturbs the spatial restriction of activin response. This is due to defects in the apicobasal polarization in the context of the polarized epithelium of the 2D gastruloid, leading to ectopic subcellular localization of TGFβ receptors. This work refines the earliest developmental window for the prodromal phase of HD to the first 2 weeks of human development, as modeled by our 2D gastruloids.

Isolated Intraspinal Neurenteric Cyst, Mimicking Arachnoid Cyst: A Case Report

Neurenteric cysts account for 0.7-1.3% of spinal axis tumors. These uncommon lesions results from the inappropriate partitioning of the embryonic notochordal plate and presumptive endoderm during the third week of human development. Heterotopic nests of epithelium reminiscent of gastrointestinal and respiratory tissue lead to eventual formation of compressive cystic lesions of the pediatric and adult spine. We report a 40-year-old male presenting with slow-progressive myelopathic manifestation and ovoid non-enhancing cysticintradural extramedullary lesion at C7 level on MRI, mimicking intraspinal arachnoid cyst, who underwent successful surgical excision. The histopathological examination prove it to be neurenteric cyst.

Familial syndromes associated with neuroendocrine tumours.

Neuroendocrine tumours may be associated with familial syndromes. At least eight inherited syndromes predisposing to endocrine neoplasia have been identified. Two of these are considered to be major factors predisposing to benign and malignant endocrine tumours, designated multiple endocrine neoplasia type 1 and type 2 (MEN1 and MEN2). Five other autosomal dominant diseases show more heterogeneous clinical patterns, such as the Carney complex, hyperparathyroidism-jaw tumour syndrome, Von Hippel-Lindau syndrome (VHL), neurofibromatosis type 1 (NF1) and tuberous sclerosis. The molecular and cellular interactions underlying the development of most endocrine cells and related organs represent one of the more complex pathways not yet to be deciphered. Almost all endocrine cells are derived from the endoderm and neuroectoderm. It is suggested that within the first few weeks of human development there are complex interactions between, firstly, the major genes involved in the initiation of progenitor-cell differentiation, secondly, factors secreted by the surrounding mesenchyme, and thirdly, a series of genes controlling cell differentiation, proliferation and migration. Together these represent a formula for the harmonious development of endocrine glands and tissue.

Cosmological dark matter and ensoulment

Allocortical structures such as hippocampal formation and amygdala are involved in the emotions and memory, and regarded as the seat of personhood. Human body is a composite of a biological organism and an intellective soul. It was suggested that cerebral allocortex is the main region harboring the soul and the beginning of a human person as an individual living organism is at the 13th week of development when an adult type allocortex is already formed. No experimental data can be sufficient to bring us to the recognition of a soul, but there must be a substance as the basis of personal identity, for without space-occupying substance, there would be no way to account for the soul’s ability to interact with the body. It was suggested that the soul substance consists of cosmological dark matter. The dark matter constitutes most of the mass in our universe, but its nature remains unknown. The soul is likely to work into man’s physical body directly via that dark matter. We thought that while the soul has a material component as dark matter, there must be an open window to the brain for the entrance of the soul with dark matter. In this respect, vomeronasal organ which is found in the nasal cavity and which has connections with the brain only between the 12th and 14th weeks of human development - a period including the time of ensoulment at 13th week - seems to be the most appropriate window through which the soul and dark matter can enter the brain.

Maternal depression and infant birth measures relate to how neonates respond to music

Two-week-old full-term newborns (26 born to depressed mothers and 26 born to non-depressed mothers) were videotaped for three 2-min intervals during: (1) a baseline silent period, (2) the playing of a musical lullaby and, (3) the lullaby with vocals added. More maternal depression symptoms were associated with more obstetric complications and newborns spending less time awake during the two music intervals. When the lullaby was played, infants born to mothers with more obstetric complications cried more and made more facial expressions. Infants who made more facial expressions at baseline spent more time awake during the musical lullaby with vocals but showed more distress, whereas fewer facial expressions indicated greater attention. Greater birthweight was related to sleeping longer during baseline, but spending more time awake and making fewer facial expressions during the musical lullaby without voice. The findings are discussed in terms of potential factors that may relate to infant music preferences in the very early weeks of human development.

Differential gene expression profiles between human embryo on day-3 and trophoblast cells on day-5: specific molecular signature

OBJECTIVE: The first week of human development is marked by the differentiation of the early embryo into the inner cell mass (ICM) and trophectoderm (TE). Whereas the oocytes, embryos and human embryonic stem cells (hESC) derived from ICM, have been particularly studied, the TE is still largely unexplored. Here, we report the human TE transcriptome by whole genome expression profiling, and we compare this transciptome with that of the embryo on day-3.

Neurenteric cysts of the spine

Neurenteric cysts account for 0.7-1.3% of spinal axis tumors. These rare lesions result from the inappropriate partitioning of the embryonic notochordal plate and presumptive endoderm during the third week of human development. Heterotopic rests of epithelium reminiscent of gastrointestinal and respiratory tissue lead to eventual formation of compressive cystic lesions of the pediatric and adult spine. Histopathological analysis of neurenteric tissue reveals a highly characteristic structure of columnar or cuboidal epithelium with or without cilia and mucus globules. Patients with symptomatic neurenteric cysts typically present in the second and third decades of life with size-dependent myelopathic and/or radicular signs. Magnetic resonance imaging and computed tomography are essential diagnostic tools for the delineation of cyst form and overlying osseous architecture. A variety of approaches have been employed in the treatment of neurenteric cysts each with a goal of total surgical resection. Although long-term outcome analyses are limited, data available indicate that surgical intervention in the case of neurenteric cysts results in a high frequency of resolution of neurological deficit with minimal morbidity. However, recurrence rates as high as 37% have been reported with incomplete resection secondary to factors such as cyst adhesion to surrounding structure and unclear dissection planes. Here we present a systematic review of English language literature from January 1966 to December 2009 utilizing MEDLINE with the following search terminology: neurenteric cyst, enterogenous cyst, spinal cord tumor, spinal dysraphism, intraspinal cyst, intramedullary cyst, and intradural cyst. In addition, the references of publications returned from the MEDLINE search criteria were surveyed in order to examine other pertinent reports.

Correlation of Embryonic Fusion Planes with the Anatomical Distribution of Basal Cell Carcinoma

The clinical relevance of the anatomic distribution of basal cell carcinoma is not completely understood. Embryonic fusion planes--the regions of mesenchymal migration and fusion of the five primordial facial processes during the 5th to 10th weeks of human development--have been implicated in the pathogenesis of basal cell carcinoma. This study sought to examine the predilection of midfacial basal cell carcinoma for cutaneous anatomical sites correlated to embryonic fusion planes. Using archived digital images and a detailed anatomic diagram, cases of basal cell carcinoma were coded according to their specific location and were aggregated into two anatomic domains according to their correlation to embryonic fusion planes. The relative tumor densities were calculated. Of the 1,457 cases examined, 859 were located in the midface. Thirty-five percent of the midfacial lesions were located on the domain correlated to embryonic fusion planes, which represented 11.3% of the total surface area of the midface. The relative tumor density of lesions in the fusion plane domain was 3.06 compared to 0.74 for the remaining lesions (p< .001). Although there is no consensus about the importance of anatomic location in the pathogenesis of basal cell carcinoma, these data indicate that, after adjusting for surface area, basal cell carcinoma was more than four times more likely to occur on an embryonic fusion plane than on other regions of the midface. These data support the possibility of an embryologic role for the pathogenesis of basal cell carcinoma.

The changing cellular environments of hematopoiesis in human development in utero

The hematopoietic system is indispensable from the earliest stages of development and adapts to the rapidly changing anatomy of the embryo and fetus; this takes place in such different anatomic locations as the yolk sac blood island, hepatic parenchyme, aorta-gonads-mesonephros paravascular mesenchyme, and bone marrow primary logette. We herein summarize our investigation of these serial blood-forming events in the human embryo and fetus. The access to early stages of human development, availability of a large panoply of molecular markers for human blood cell lineages, and recent development of robust assays for the earliest human hematopoietic stem cells have allowed us to gain relatively clear insight into the developmental sequence that underlies the ontogeny of human blood cells. Conversely, the control exerted by these diverse cellular environments on the emergence of human hematopoietic cells remains elusive, as is the case in animal models. We nonetheless present preliminary attempts to decipher the structure and molecular characteristics of the distinct cellular "niches" in which blood cells are produced during human gestation.

Gene expression in pharyngeal arch 1 during human embryonic development

Craniofacial abnormalities are one of the most common birth defects in humans, but little is known about the human genes that control these important developmental processes. To identify relevant genes, we analyzed transcription profiles of human pharyngeal arch 1 (PA1), a conserved embryonic structure that develops into the palate and jaw. Using microdissected, normal human craniofacial structures, we constructed 12 SAGE (serial analysis of gene expression) libraries and sequenced 606 532 tags. We also performed Affymetrix microarray analysis on 25 craniofacial targets. Our data revealed not only genes "enriched" or differentially expressed in PA1 during fourth and fifth week of human development, but also 6927 genes newly identified to be expressed in human PA1. Many of these genes are involved in biosynthetic processes and have binding function and catalytic activity. We compared expression profiles of human genes with those of mouse homologs to look for genes more specific to human craniofacial development and found 766 genes expressed in human PA1, but not in mouse PA1. We also identified 1408 genes that were expressed in mouse as well as human PA1 and could be useful in creating mouse models for human conditions. We confirmed conservation of some human PA1 expression patterns in mouse embryonic samples with whole mount in situ hybridization and real-time RT-PCR. This comprehensive approach to expression profiling gives insights into the early development of the craniofacial region and provides markers for developmental structures and candidate genes, including SET and CCT3, for diseases such as orofacial clefting and micrognathia.

Evolution of heart disease in utero.

Cardiac embyogenesis occurs in the first 6 to 7 weeks of human development. Although it is during this time that many of the major cardiovascular defects develop, many of these lesions continue to evolve and others develop in the latter half of gestation. There may be development or progression of ventricular inflow or outflow tract and arch obstruction, and ventricular or great artery hypoplasia. There may be progressive antrioventricular or semi-lunar valve regurgitation which can compromise the fetal circulation. There may be development of dysrhythmias, primary myocardial disease and heart failure. The fetal shunts, the foramen ovale and ductus arteriosus, may change in form and function. Finally, cardiac tumors may develop, grow, or regress. Knowledge of the mechanisms of and potential for progression in fetal heart disease is critical for counseling regarding prognosis and for planning of prenatal and neonatal management.

Cardiac myosin binding protein C gene is specifically expressed in heart during murine and human development.

Cardiac myosin binding protein C (MyBP-C) is a substantial component of the sarcomere, with both structural and regulatory roles. The gene encoding cardiac MyBP-C in humans is located on chromosome 11p11.2, and mutations that are most predicted to produce truncated proteins have been identified in this gene in unrelated families with familial hypertrophic cardiomyopathy (FHC). To understand better the pathophysiology of FHC and with a view to the development of animal models for this disease, we have investigated by in situ hybridization the pattern of expression of the cardiac MyBP-C gene during human and mouse development using species-specific oligonucleotide probes. From 4 weeks of human development, a strong labeling of cardiac MyBP-C mRNAs was unambiguously detected in all heart compartments, and no signal could be visualized in somites. In murine embryos, from embryonic day 9.5 until birth, a strong signal was detected exclusively in the heart. Our results showed that during both human and murine development, in contrast to chicken development, the cardiac MyBP-C gene is abundantly and specifically expressed in the heart.

Recent advances in primary palate and midface morphogenesis research.

During the sixth week of human development, the primary palate develops as facial prominences enlarge around the nasal pits to form the premaxillary region. Growth of craniofacial components changes facial morphology and affects the extent of contact between the facial prominences. Our recent studies have focused on developing methods to analyze growth of the primary palate and the craniofacial complex to define morphological phases of normal development and to determine alterations leading to cleft lip malformation. Analysis of human embryos in the Carnegie Embryology Collection and mouse embryos of cleft lip and noncleft strains showed that human and mouse embryos have similar phases of primary palate development: first, an epithelial seam, the nasal fin, forms; then a mesenchymal bridge develops through the nasal fin and enlarges rapidly. A robust mesenchymal bridge must form between the facial prominences before advancing midfacial growth patterns tend to separate the facial components as the medial nasal region narrows and elongates, the nasal pits narrow, and the primary choanae (posterior nares) open posterior to the primary palate. In mouse strains with cleft lip gene, maxillary growth, nasal fin formation, and mesenchymal replacement of the nasal fin were all delayed compared with noncleft strains of mice. Successful primary palate formation involves a sequence of local cellular events that are closely timed with spatial changes associated with craniofacial growth that must occur within a critical developmental period.

Human airway secretory cells during development and in mature airway epithelium

The combined secretions of distinct secretory cells of the airway lining mucosa serve to keep the inspired air moist and free of potentially harmful dust particles, organisms and adsorbed gases. Apart from their role in protecting the respiratory zone of the lung, mucus-secreting cells act as pluripotential stem cells during foetal development and, in the adult, following mucosal injury. The variety of secretory cells include the mucous and serous cells of the surface and glandular epithelium, the non-ciliated bronchiolar (Clara) cell and the less frequent dense-core granulated (neuroendocrine) cell. The last-mentioned is the first type to differentiate at about 10 weeks of gestation; mucus-secreting cells are present from the 13th week of gestation, when mature ciliated cells are already present, and Clara cells begin to mature during the 19th week of human development. The alteration of secretory cell number and chemical composition of their secretions during the second trimester of foetal life is similar to that which occurs in chronic bronchitis in the adult. However, in hypersecretory disease the extent and site of the major change appear to be inappropriate to the defence of the lung.

Distribution of transforming growth factor beta in a two-week-old human embryo.

Using immunohistochemical methods we have investigated the presence of transforming growth factors beta 1, beta 2 and beta 1 precursor in a two-week-old bilaminar human embryo. TGF-beta 1 precursor was seen in both the epiblast and the hypoblast. In contrast to the widespread localization of TGF-beta 1 precursor in the embryo proper, antibodies to the mature TGF-beta 1 peptide localized preferentially to the hypoblast with only weak staining in the epiblast. Staining with antibodies to TGF-beta 2 was generally weak in both the epiblast and hypoblast layers of the embryo proper. These results show that TGF-beta 1 and beta 2 peptides are detectable as early as the second week of human development.

Hypoglycemia: How little is too much for the embryo?

The effects of hypoglycemia on mammalian embryos undergoing neurulation (third to fourth week of human development) were investigated. Mouse embryos were maintained for 28 hours in whole embryo culture in serum collected from rats that had received 50 units of 100 United States Pharmacopeia insulin units per milliliter. Glucose concentrations used were 40, 60, 80, and 147 mg/dl (normal blood glucose in the pregnant mouse is 125 mg/dl). After the culture period embryos were evaluated for malformations and growth and compared with those maintained under euglycemic conditions. The results demonstrate that glucose concentrations approximately 50% of normal maternal levels were teratogenic but not growth inhibitory, whereas concentrations in the range of 30% to 40% of maternal levels were lethal to the embryo. Furthermore, a 14-hour exposure to reduced blood sugar in either the first or second half of the culture period produced malformations.