Differential gene expression during early murine yolk sac development

The visceral yolk sac (VYS), composed of extraembryonic mesoderm and visceral endoderm, is the initial site of blood cell development and serves important nutritive and absorptive functions. In the mouse, the visceral endoderm becomes a morphologically distinct tissue at the time of implantation (E4.5), while the extraembryonic mesoderm arises during gastrulation (E6.5–8.5). To isolate genes differentially expressed in the developing yolk sac, polymerase chain reaction (PCR) methods were used to construct cDNA from late primitive streak to neural plate stage (E7.5) murine VYS mesoderm and VYS endoderm tissues. Differential screening led to the identification of six VYS mesoderm-enriched clones: ribosomal protein L13a, the heat shock proteins hsc 70 and hsp 86, guanine-nucleotide binding protein-related gene, cellular nucleic acid binding protein, and ã-enolase. One VYS endoderm-specific cDNA was identified as apolipoprotein C2. In situ hybridization studies confirmed the differential expression of these genes in E7.5 yolk sac tissues. These results indicate that representative cDNA populations can be obtained from small numbers of cells and that PCR methodologies permit the study of gene expression during early mammalian postimplantation development. While all of the mesoderm-enriched genes were ubiquitously expressed in the embryo proper, apolipoprotein C2 expression was confined to the visceral endoderm. These results are consistent with the hypothesis that at E7.5, the yolk sac endoderm provides differentiated liver-like functions, while the newly developing extraembryonic mesoderm is still a largely undifferentiated tissue. © 1995 wiley-Liss, Inc.     

Differential expression of the cellular src gene during vertebrate development

Cellular genes that are homologous to the transforming genes of certain RNA tumor viruses are suspected to play a functional role during normal developmental processes. To investigate this further, we are studying the expression of the cellular homolog of the Rous sarcoma virus transforming gene (c-src) during embryogenesis of fish, frog, and chicken by quantitative determination of the activity of the c-src encoded protein kinase (pp60^c-src). The kinase activity from embryos of fish, frog, and chicken displays the same enzymatic characteristics as the kinase from adult animals: It phosphorylates only tyrosine residues in protein substrates, and its activity is relatively insensitive to inhibition by the diadenosine nucleotide Ap4A. During the course of development, the varying kinase activity level reflects differential expression of the c-src gene product. The kinase activity is low during early development, increases dramatically during organogenesis, and decreases thereafter to the level found in adult animals. The kinase activity displays an organ specificity, with brain showing the highest activity in embryos as well as in adults. Muscle, however, shows high activities during organogenesis, but no or barely detectable activity in adult animals. Our data suggest, therefore, that the c-src gene product plays more of a role in differentiation than in proliferation processes during embryogenesis, and that it may act as a pleiotropic effector.     

Differential spatio-temporal expression of alpha-dystrobrevin-1 during mouse development

Dystrobrevins are a family of dystrophin-related and dystrophin-associated proteins. alpha-dystrobrevin-1 knockout mice suffer from skeletal and cardiac myopathies. It has been suggested that the pathology is caused by the loss of signalling functions but the exact role of dystrobrevins is largely unknown. We have analysed the spatial and temporal expression of alpha-dystrobrevin-1 during mouse embryogenesis and found striking developmental regulation and distribution patterns. During development this protein was expressed not only in muscle but also in the CNS, sensory organs, epithelia and skeleton. Particularly interesting was the correlation of alpha-dystrobrevin-1 expression with the induction of various differentiation processes in the developing eye, inner ear, pituitary, blood-brain barrier, stomach epithelium and areas of the brain, dorsal root ganglia and spinal cord. In contrast, this specific expression at the induction phase decreased/disappeared at later stages of development.     

Differential usage of photoreceptors for chalcone synthase gene expression during plant development

Photoregulation of chalcone synthase (CHS) mRNA accumulation was analysed in parsley (Petroselinum crispum) and mustard (Sinapis alba) plants at different developmental stages. In both species, CHS mRNA accumulation in young etiolated seedlings was primarily under phytochrome control. In leaves of adult re-etiolated plants, a UV-B photoreceptor was predominantly involved in photocontrol. The reduced red light control in mature leaves was not due to the absence of immunoreactive phytochrome. The apparent dependence of photoreceptor usage on the developmental state of the cell or organism was in accordance with observations on the photoregulation of fusion constructs between CHS promoters from parsley or mustard and the β-glucuronidase reporter gene (GUS). When tested in the parsley protoplast transient expression system, both constructs yielded the same type of photoregulation as observed for the endogenous CHS gene.     

Differential expression pattern of coq-8 gene during development in Caenorhabditis elegans

Coenzyme Q (Q) and the genes involved in its biosynthesis are involved in aging and development of Caenorhabditis elegans. Q is synthesized by at least eight highly conserved nuclear coq genes, but this biosynthesis pathway and its regulation is not known. The coq-8 gene sequence has homology to the ABC-1 family kinases and is the only known candidate for a possible regulation of this pathway. To study coq-8 expression pattern, we have developed a C. elegans transgenic strain expressing ubiquinone biosynthesis coq-8 gene promoter and GFP construct. We show here an age-dependent specific pattern from embryo to senescence for COQ-8 protein expression. Expression in embryo was triggered by a defined group of blastomers before morphogenesis. In elderly nematodes expression was only observed in nervous system, whilst expression in larvae was also detected in hypodermis, muscles and coelomocytes. Global expression provide a regulated pattern during life cycle of the nematode.     

Differential expression of the glycosylated forms of MUC1 during lung development

Human MUC1 mucin is a high-molecular weight transmembrane glycoprotein expressed on the apical surface of the simple epithelia of many different tissues. Previous investigations suggest the involvement of MUC1 in epithelial cytodifferentiation and glandular morphogenesis. However, the role of MUC1 in the development of the fetal respiratory tracts has so far been poorly investigated. To obtain more information on the roles of MUC1 during fetal lung development, we examined the expression and distribution of MUC1 by immunohistochemical staining of postmortem lung specimens from fetuses and neonates of various gestational ages. Three monoclonal antibodies, HMFG1, HMFG2, and anti-KL-6, which bind different glycosylation variants, were used. Each monoclonal antibody has been shown to recognize heavily-glycosylated MUC1, sparsely-glycosylated MUC1, and sialylated carbohydrate side chains of MUC1, respectively. At 13 weeks of gestation, the terminal respiratory tracts were diffusely stained with HFMG1 and anti-KL-6. Sparsely-glycosylated MUC1, as recognized by HMFG2, was detected only in the distal portions of the terminal bronchioles that divided into respiratory bronchioles. As such development continued, MUC1, recognized by HMFG1 and anti-KL-6, was detected throughout the bronchioles and terminal sacs, although HMFG1 immunoreactivity decreased in intensity towards the terminal sacs. Sparsely-glycosylated MUC1, as recognized by HMFG2, was mainly observed in the terminal portions. In the adult lungs, both the alveolar spaces and the respiratory bronchioles stained with HFMG1 and anti-KL-6. However, the distribution of sparsely-glycosylated MUC1 was limited in the alveolar epithelial cells. Our investigation demonstrated that variants of MUC1 were expressed in the fetal respiratory tracts as early as 13 weeks of gestation, and its expression persisted even after lung maturation. The precise roles of MUC1 were not determined in the present study; however, different glycosylation variants of MUC1 may be associated with the development of different regions of the terminal respiratory tract.     

Differential gene expression during Trypanosoma cruzi metacyclogenesis

The transformation of epimastigotes into metacyclic trypomastigotes involves changes in the pattern of expressed genes, resulting in important morphological and functional differences between these developmental forms of Trypanosoma cruzi. In order to identify and characterize genes involved in triggering the metacyclogenesis process and in conferring to metacyclic trypomastigotes their stage specific biological properties, we have developed a method allowing the isolation of genes specifically expressed when comparing two close related cell populations (representation of differential expression or RDE). The method is based on the PCR amplification of gene sequences selected by hybridizing and subtracting the populations in such a way that after some cycles of hybridization-amplification genes specific to a given population are highly enriched. The use of this method in the analysis of differential gene expression during T. cruzi metacyclogenesis (6 hr and 24 hr of differentiation and metacyclic trypomastigotes) resulted in the isolation of several clones from each time point. Northern blot analysis showed that some genes are transiently expressed (6 hr and 24 hr differentiating cells), while others are present in differentiating cells and in metacyclic trypomastigotes. Nucleotide sequencing of six clones characterized so far showed that they do not display any homology to gene sequences available in the GeneBank.     

Variation in gene expression patterns in human gastric cancers

Gastric cancer is the world's second most common cause of cancer death. We analyzed gene expression patterns in 90 primary gastric cancers, 14 metastatic gastric cancers, and 22 nonneoplastic gastric tissues, using cDNA microarrays representing approximately 30,300 genes. Gastric cancers were distinguished from nonneoplastic gastric tissues by characteristic differences in their gene expression patterns. We found a diversity of gene expression patterns in gastric cancer, reflecting variation in intrinsic properties of tumor and normal cells and variation in the cellular composition of these complex tissues. We identified several genes whose expression levels were significantly correlated with patient survival. The variations in gene expression patterns among cancers in different patients suggest differences in pathogenetic pathways and potential therapeutic strategies.     

Expression of the SMADIP1 gene during early human development

There are four members of the platelet-derived growth factor (PDGF) family; PDGF-A, PDGF-B, PDGF-C and PDGF-D. Their biological effects are mediated via two tyrosine kinase receptors, PDGFR-alpha and PDGFR-beta, and PDGF-mediated signaling is critical for development of many organ systems. Analysis in adult tissues showed that PDGF-C was mainly expressed in kidney, testis, liver, heart and brain. During development, PDGF-C expression was widespread and dynamic, and found in somites and their derivatives, in kidney, lung, brain, and in several other tissues, particularly at sites of developing epidermal openings. PDGF-C may therefore have unique functions during tissue development and maintenance.     

Differential gene expression profiling in blood from patients with digestive system cancers

To develop a non-invasive and sensitive diagnostic test for cancer using peripheral blood, we evaluated gene expression profiling of blood obtained from patients with cancer of the digestive system and normal subjects. The expression profiles of blood-derived total RNA obtained from 39 cancer patients (11 colon cancer, 14 gastric cancer, and 14 pancreatic cancer) was clearly different from those obtained from 15 normal subjects. By comparing the gene expression profiles of cancer patients and normal subjects, 25 cancer-differentiating genes (p < 5.0 × 10⁻⁶ and fold differences >3) were identified and an “expression index” deduced from the expression values of these genes differentiated the validation cohort (11 colon cancer, 8 gastric cancer, 18 pancreatic cancer, and 15 normal subjects) into cancer patients and normal subjects with 100% (37/37) and 87% (13/15) accuracy, respectively. Although, the expression profiles were not clearly different between the cancer patients, some characteristic genes were identified according to the stage and species of the cancer. Interestingly, many immune-related genes such as antigen presenting, cell cycle accelerating, and apoptosis- and stress-inducing genes were up-regulated in cancer patients, reflecting the active turnover of immune regulatory cells in cancer patients. These results showed the potential relevance of peripheral blood gene expression profiling for the development of new diagnostic examination tools for cancer patients.     

Differential expression of Eya1 and Eya2 during chick early embryonic development

Eyes absent is essential for compound eye formation in Drosophila. Its mammalian homologues of Eya are involved in the development of sensory organs, skeletal muscles and kidneys. Mutations of EYA1 in human cause branchio-oto-renal syndrome, with abnormalities in branchial derivatives, ear and kidney. For an insight into the function of Eya1 and Eya2 in early development, we performed whole-mount in situ hybridization and compared the expression patterns of these two genes in the developing chick embryos. Eya1 was first expressed in the primitive streak at Hamburger and Hamilton stage 4 (HH4) and appeared in the ectoderm and head mesenchyme distinct from migrating neural crest cells at HH6-HH11. At HH15 and HH17, the olfactory, otic and vagal/nodose placodes and cranial ganglia were positive for Eya1. In contrast, Eya2 was already expressed in the endoderm at HH4, and appeared in the endoderm and prospective placodal region at HH6-HH11. Eya2 expression was observed in pharyngeal clefts and pouches as well as cranial placodes at HH15 and HH17. These results indicate differential expression of Eya1 and Eya2, both spatially and temporally, in chick during early development. The expression patterns are somewhat different from those of other species such as Xenopus, zebrafish and mouse. The results suggest distinct and unique functions for Eya1 and Eya2 in early chick development.