Embryology

Embryology (from Greek ἔμβρυον, embryon, "the unborn, embryo"; and -λογία, -logia) is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses. Additionally, embryology encompasses the study of congenital disorders that occur before birth, known as teratology. Early embryology was proposed by Marcello Malpighi, and known as preformationism, the theory that organisms develop from pre-existing miniature versions of themselves. Aristotle proposed the theory that is now accepted, epigenesis. Epigenesis is the idea that organisms develop from seed or egg in a sequence of steps. Modern embryology developed from the work of Karl Ernst von Baer, though accurate observations had been made in Italy by anatomists such as Aldrovandi and Leonardo da Vinci in the Renaissance. As recently as the 18th century, the prevailing notion in western human embryology was preformation: the idea that semen contains an embryo – a preformed, miniature infant, or homunculus – that simply becomes larger during development. The competing explanation of embryonic development was epigenesis, originally proposed 2,000 years earlier by Aristotle. Much early embryology came from the work of the Italian anatomists Aldrovandi, Aranzio, Leonardo da Vinci, Marcello Malpighi, Gabriele Falloppio, Girolamo Cardano, Emilio Parisano, Fortunio Liceti, Stefano Lorenzini, Spallanzani, Enrico Sertoli, and Mauro Ruscóni. According to epigenesis, the form of an animal emerges gradually from a relatively formless egg. As microscopy improved during the 19th century, biologists could see that embryos took shape in a series of progressive steps, and epigenesis displaced preformation as the favored explanation among embryologists. 'CLEVAGE' Cleavage is the very beginning steps of a developing embryo. Cleavage refers to the many mitotic divisions that occur after the egg is fertilized by the sperm. The ways in which the cells divide is specific to certain types of animals and may have many forms.

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related categories (217)

Related concepts (99)

Related courses (1)

Related lectures (12)

Related people (6)

Related publications (71)

BIO-221: Cell and developmental biology for engineers

Students will learn essentials of cell and developmental biology with an engineering mind set, with an emphasis on animal model systems and quantitative approaches.

Yolk sac

The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though yolk sac is far more widely used. In humans, the yolk sac is important in early embryonic blood supply, and much of it is incorporated into the primordial gut during the fourth week of embryonic development. The yolk sac is the first element seen within the gestational sac during pregnancy, usually at 3 days gestation.

Small for gestational age

Small for gestational age (SGA) newborns are those who are smaller in size than normal for the gestational age. SGA is most commonly defined as a weight below the 10th percentile for the gestational age. SGA predicts susceptibility to hypoglycemia, hypothermia, and polycythemia. By definition, at least 10% of all newborns will be labeled SGA. All SGA babies should be watched for signs of failure to thrive, hypoglycemia and other health conditions.

Gastroschisis

Gastroschisis is a birth defect in which the baby's intestines extend outside of the abdomen through a hole next to the belly button. The size of the hole is variable, and other organs including the stomach and liver may also occur outside the baby's body. Complications may include feeding problems, prematurity, intestinal atresia, and intrauterine growth restriction. The cause is typically unknown. Rates are higher in babies born to mothers who smoke, drink alcohol, or are younger than 20 years old.

Diverse cell-specific patterns of alternative polyadenylation in Drosophila

Bart Deplancke, Sandy Lee

Most genes in higher eukaryotes express isoforms with distinct 3' untranslated regions (3' UTRs), generated by alternative polyadenylation (APA). Since 3' UTRs are predominant locations of post-transcriptional regulation, APA can render such programs conditional, and can also alter protein sequences via alternative last exon (ALE) isoforms. We previously used 3'-sequencing from diverse Drosophila samples to define multiple tissue-specific APA landscapes. Here, we exploit comprehensive single nucleus RNA-sequencing data (Fly Cell Atlas) to elucidate cell-type expression of 3' UTRs across >250 adult Drosophila cell types. We reveal the cellular bases of multiple tissue-specific APA/ALE programs, such as 3' UTR lengthening in differentiated neurons and 3' UTR shortening in spermatocytes and spermatids. We trace dynamic 3' UTR patterns across cell lineages, including in the male germline, and discover new APA patterns in the intestinal stem cell lineage. Finally, we correlate expression of RNA binding proteins (RBPs), miRNAs and global levels of cleavage and polyadenylation (CPA) factors in several cell types that exhibit characteristic APA landscapes, yielding candidate regulators of transcriptome complexity. These analyses provide a comprehensive foundation for future investigations of mechanisms and biological impacts of alternative 3' isoforms across the major cell types of this widely-studied model organism.

NATURE PORTFOLIO2022

The role of the Nimrod proteins in the Drosophila immune system

Bianca Marie Petrignani

The use of tractable model organisms such as Drosophila melanogaster and the powerful genetic tools they offer has contributed significantly to recent advances in comprehension of innate immunity, notably phagocytosis. To date, several phagocytic transmembrane receptors, opsonins, and ligands have been discovered in Drosophila melanogaster. Many of them belong to the Nimrod family, which includes both secreted and transmembrane proteins containing several NIM repeats. Genetic and biochemical studies have revealed the roles of transmembrane Nimrod receptors such as Draper, Simu and Eater in phagocytosis. However, the function of the five secreted Nimrod members, the Nimrod B proteins, remains unstudied. The goals of my thesis were to characterize the function of the secreted Nimrod B proteins using newly generated CRISPR-Cas9 null mutations, focusing on NimB5, NimB4, and NimB1 genes. In this work, we first found that the secreted protein, NimB5, is produced in the fat body upon nutrient scarcity downstream of metabolic sensors and ecdysone signaling. We provide evidence that NimB5 binds to hemocytes to down-regulate their proliferation and adhesion. Blocking this signaling loop results in conditional lethality when larvae are raised on a poor diet due to excessive hemocyte numbers and insufficient energy storage. This pointed to a role of NimB5 in the allocation of resources to blood cells, tailoring the investment in the immune system to metabolic resource availability.In the second part of this thesis, we analyzed the function of NimB4 to reveal its crucial role in clearance of apoptotic cells. NimB4 is expressed by macrophages and glial cells, the two main types of phagocytes in Drosophila. Our study points to a role of NimB4 in phagosome maturation, more specifically in the fusion between the phagosome and lysosomes. We propose that similar to bridging molecules, NimB4 binds to apoptotic corpses to engage a phagosome maturation program dedicated to efferocytosis. Finally, in the last part of the thesis, we present preliminary results on the role of NimB1 in the Drosophila immune system. NimB1 is expressed mainly in hemocytes and regulates hemocyte number. Additionally, NimB1 shares several characteristics with NimB4, notably the ability to bind to apoptotic cells. As such, we hypothesize that it could play a similar function in the phagocytosis of apoptotic cells. However, the exact role of NimB1 in phagocytosis is still unclear, and additional work is necessary to understand if NimB1 plays a role in the uptake of apoptotic cells or phagosome maturation. Collectively, this thesis has revealed that the NimB proteins play specific roles in efferocytosis or in blood cell number regulation. Thus, this work extended our knowledge on the Drosophila cellular immune response by providing new insight on the conserved Nimrod family of proteins.

EPFL2022

KRAB zinc finger protein-mediated control of transposon-embedded regulatory sequences from human germline to early embryos

Alexandra Iouranova

Transposable elements (TEs), also called jumping genes, are genetic elements capable of changing their position within the genome of their host. They make up large fractions of genomes, including 45% of human DNA content, according to current estimates. Some of these elements are of retroviral origin and are known as endogenous retroviruses (ERVs). Long terminal repeats (LTRs) of ERVs, like other TEs, influence host gene expression in various ways. They can for example create new promoters, enhancers or imprinted regions upon integration. As ERVs derive from a germline infection in the common ancestor of a species, they are often restricted to a particular evolutionary clade. While rewiring by TEs can harm a host genome, some of the features of TE invasions can increase host fitness and appear to be universally exploited by various organisms. For instance, TE insertions happen faster than protein-coding genes evolve. They can therefore be coopted for a species-specific evolutionary remodeling of transcriptional networks. Specifically, the LTR12/ERV9 TE family has colonized primate genomes over the past 30 million years and has been widely reported to contribute regulatory elements to the human genome. In this work, we set out to establish the features that made this family successful, and to assess the prevalence of LTR12-derived regulatory elements in early development. We observe the hominoid-restricted LTR12C subfamily to be a driver of transcription in both gametogenesis and early embryogenesis. LTR12C loci have rewired genes involved in ciliogenesis and flagellogenesis that are critical for male fertility. Relatedly, they also present unusual behavior during the epigenetic reprogramming characteristic of these periods by resisting genome-wide demethylation in primordial germ cell (PGC) development. To identify the determinants of the epigenetic status of LTR12C elements that made them attractive for cooption, we turn to KRAB zinc finger proteins (KZFPs). TEs appear to be prominent targets of this large family of epigenetic repressors. Through functional studies, we determine ZNF676 is a regulator of LTR12C, with its targets resisting genome-wide demethylation. This resistance possibly pre-marks them for zygotic rather than maternal expression. We show that ZNF676 levels influence the expression of some cilium-related genes and are able to disrupt ciliogenesis. We conclude this KZFP likely coevolved with its target ERVs, which carried its binding sites into the vicinity of multiple genes, including those important for male fertility. KZFPs can therefore become regulators of genes with a common function along with the transposable elements they target. More generally, in our study of TEs expressed in human embryonic development, we find the expression of some TE families to be a hallmark of a particular development stage, an indicator of the current chromatin state. These markers provide a criterion that can be used to assess the similarity of embryonic development models to real embryos. Transcription of some marker TEs anticorrelates with that of their putative KZFP regulators, implying proper KZFP expression to be important to properly recapitulate embryonic development. Our results provide insight into the TE- and KZFP-mediated rewiring of transcriptional networks related to the germline and early development, and suggest that the improper expression of a KZFP can have consequences ranging up to infertility.

EPFL2021

Explores causal inference in epidemiology, focusing on COVID-19's impact on preterm birth and refining treatment strategies for prostate cancer.

Explores human embryology from fertilization to blastocyst formation, emphasizing its importance for careers in biology and medicine.

Covers Gestational Diabetes Mellitus (GDM), its diagnosis, treatment options, and associated risks for both the mother and the offspring.

Topics in endocrinology

Endocrinology (from endocrine + -ology) is a branch of biology and medicine dealing with the endocrine system, its diseases, and its specific secretions known as hormones. It is also concerned with the integration of developmental events proliferation, growth, and differentiation, and the psychological or behavioral activities of metabolism, growth and development, tissue function, sleep, digestion, respiration, excretion, mood, stress, lactation, movement, reproduction, and sensory perception caused by hormones.

Reproductive biology

Reproductive biology includes both sexual and asexual reproduction. Reproductive biology includes a wide number of fields: Reproductive systems Endocrinology Sexual development (Puberty) Sexual maturity Reproduction Fertility Human reproduction Endocrinology Human reproductive biology is primarily controlled through hormones, which send signals to the human reproductive structures to influence growth and maturation. These hormones are secreted by endocrine glands, and spread to different tissues in the human body.

Topics in gynaecology

Gynaecology or gynecology (see American and British English spelling differences) is the area of medicine that involves the treatment of women's diseases, especially those of the reproductive organs. It is often paired with the field of obstetrics, forming the combined area of obstetrics and gynaecology (OB-GYN). The term comes from Greek and means "the science of women". Its counterpart is andrology, which deals with medical issues specific to the male reproductive system.