30 research outputs found
Patterning of the C. elegans 1° vulval lineage by RAS and Wnt pathways
In C. elegans, the descendants of the 1° vulval precursor
cell (VPC) establish a fixed spatial pattern of two different cell fates: E-F-F-E. The two inner granddaughters attach to the somatic gonadal anchor cell (AC) and generate four vulF cells, while the two outer granddaughters produce
four vulE progeny. zmp-1::GFP, a molecular marker that
distinguishes these two fates, is expressed in vulE cells, but not vulF cells. We demonstrate that a short-range AC signal is required to ensure that the pattern of vulE and vulF fates is properly established. In addition, signaling between the inner and outer 1° VPC descendants, as well as intrinsic polarity of the 1° VPC daughters, is involved in the asymmetric divisions of the 1° VPC daughters and the
proper orientation of the outcome. Finally, we provide
evidence that RAS signaling is used during this new AC
signaling event, while the Wnt receptor LIN-17 appears to
mediate signaling between the inner and outer 1° VPC
descendants
The C. elegans LIM homeobox gene lin-11 specifies multiple cell fates during vulval development
LIM homeobox family members regulate a variety of cell fate choices during animal development. In C. elegans, mutations in the LIM homeobox gene lin-11 have previously been shown to alter the cell division pattern of a subset of the 2° lineage vulval cells. We demonstrate multiple functions of lin-11 during vulval development. We examined the fate of vulval cells in lin-11 mutant animals using five cellular markers and found that lin-11 is necessary for the patterning of both 1° and 2° lineage cells. In the absence of lin-11 function, vulval cells fail to acquire correct identity and inappropriately fuse with each other. The expression pattern of lin-11 reveals dynamic changes during development. Using a temporally controlled overexpression system, we show that lin-11 is initially required in vulval cells for establishing the correct invagination pattern. This process involves asymmetric expression of lin-11 in the 2° lineage cells. Using a conditional RNAi approach, we show that lin-11 regulates vulval morphogenesis. Finally, we show that LDB-1, a NLI/Ldb1/CLIM2 family member, interacts physically with LIN-11, and is necessary for vulval morphogenesis. Together, these findings demonstrate that temporal regulation of lin-11 is crucial for the wild-type vulval patterning
Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases
The production of peroxide and superoxide is an inevitable consequence of
aerobic metabolism, and while these particular "reactive oxygen species" (ROSs)
can exhibit a number of biological effects, they are not of themselves
excessively reactive and thus they are not especially damaging at physiological
concentrations. However, their reactions with poorly liganded iron species can
lead to the catalytic production of the very reactive and dangerous hydroxyl
radical, which is exceptionally damaging, and a major cause of chronic
inflammation. We review the considerable and wide-ranging evidence for the
involvement of this combination of (su)peroxide and poorly liganded iron in a
large number of physiological and indeed pathological processes and
inflammatory disorders, especially those involving the progressive degradation
of cellular and organismal performance. These diseases share a great many
similarities and thus might be considered to have a common cause (i.e.
iron-catalysed free radical and especially hydroxyl radical generation). The
studies reviewed include those focused on a series of cardiovascular, metabolic
and neurological diseases, where iron can be found at the sites of plaques and
lesions, as well as studies showing the significance of iron to aging and
longevity. The effective chelation of iron by natural or synthetic ligands is
thus of major physiological (and potentially therapeutic) importance. As
systems properties, we need to recognise that physiological observables have
multiple molecular causes, and studying them in isolation leads to inconsistent
patterns of apparent causality when it is the simultaneous combination of
multiple factors that is responsible. This explains, for instance, the
decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference
Pattern formation during Caenorhabditis Elegans vulval development
Pattern formation during animal development involves at least three
processes: establishment of the competence of precursor cells to respond to
intercellular signals, formation of a pattern of different cell fates adopted by
precursor cells, and execution of the cell fate by generating a pattern of
distinct descendants from precursor cells. I have analyzed the fundamental
mechanisms of pattern formation by studying the development of
Caenorhabditis elegans vulva.
In C. elegans, six multipotential vulval precursor cells (VPCs) are
competent to respond to an inductive signal LIN-3 (EGF) mediated by LET-
23 (RTK) and a lateral signal via LIN-12 (Notch) to form a fixed pattern of 3°-3°-2°-1°-2°-3°. Results from expressing LIN-3 as a function of time in
animals lacking endogenous LIN-3 indicate that both VPCs and VPC
daughters are competent to respond to LIN-3. Although the daughters of
VPCs specified to be 2° or 3° can be redirected to adopt the 1°fate, the
decision to adopt the 1° fate is irreversible. Coupling of VPC competence to
cell cycle progression reveals that VPC competence may be periodic during
each cell cycle and involve LIN-39 (HOM-C). These mechanisms are
essential to ensure a bias towards the 1° fate, while preventing an excessive
response.
After adopting the 1° fate, the VPC executes its fate by dividing three
rounds to form a fixed pattern of four inner vulF and four outer vulE descendants.
These two types of descendants can be distinguished by a
molecular marker zmp-1::GFP. A short-range signal from the anchor cell
(AC), along with signaling between the inner and outer 1° VPC descendants
and intrinsic polarity of 1° VPC daughters, patterns the 1° lineage. The Ras
and the Wnt signaling pathways may be involved in these mechanisms.
The temporal expression pattern of egl-17::GFP, another marker ofthe
1° fate, correlates with three different steps of 1° fate execution: the
commitment to the 1° fate, as well as later steps before and after
establishment of the uterine-vulval connection. Six transcription factors,
including LIN-1(ETS), LIN-39 (HOM-C), LIN-11(LIM), LIN-29 (zinc finger),
COG-1 (homeobox) and EGL-38 (PAX2/5/8), are involved in different steps
during 1° fate execution.</p
The Caenorhabditis elegans heterochronic gene lin-29 coordinates the vulval–uterine–epidermal connections
AbstractBackground: The development of a connection between the uterus and the vulva in the nematode Caenorhabditis elegans requires specification of a uterine cell called the utse, and its attachment to the vulva and the epidermal seam cells. The uterine π cells generate the utse and uv1 cells, which also connect the uterus to the vulva. The uterine anchor cell (AC) induces the vulva through LIN-3/epidermal growth factor (EGF) signaling, and the π cells through LIN-12/Notch signaling. Here, we report that a gene required for seam cell maturation is also required for specification of the utse and for vulval differentiation, and thus helps to coordinate development of the vulval–uterine–seam cell connection.Results: We cloned the egl-29 gene, which is necessary for induction of uterine π cells, and found it to be allelic to lin-29, which encodes a zinc finger transcription factor that is necessary for the terminal differentiation of epidermal seam cells. In the uterus, lin-29 functioned upstream of lin-12 in the induction of π cells and was necessary to maintain expression in the AC of lag-2, which encodes a ligand for LIN-12.Conclusions: The lin-29 gene controls gene expression in the epidermal seam cells, uterus and vulva, and may help to coordinate the terminal development of these three tissues by regulating the timing of late gene expression during organogenesis
Polyclonal antibody preparation against candidate tumour suppressor protein MIP for detection of its expression and localization in hepatocellular carcinoma
MIP is a candidate tumour suppressor protein found in hepatocellular carcinoma. It can interact with different proteins in different subcellular locations. However, antibodies against MIP for testing purposes are still not available and this has hindered the research on MIP protein. In this study, the full coding sequence of MIP protein was cloned into the prokaryotic expression vector pET-28a. The recombinant protein his-MIP was expressed by IPTG (isopropyl β-D-1-thiogalactopyranoside) induction and purified by nickel-affinity chromatography, then used to immunize New Zealand rabbits to obtain a polyclonal antibody against MIP. The sensitivity and specificity of the antibody were evaluated by enzyme-linked immunosorbent assay and western blot. We used the obtained antibody to detect endogenous MIP protein in hepatocellular carcinoma (HCC) cells and normal human hepatic cells L-O2 and found decreased MIP expression in HCC cells. The immunohistochemistry results further showed that the expression level of MIP protein in HCC tissues was lower than that in the corresponding adjacent non-cancerous tissues. The MIP protein was distributed mainly in the cytoplasm in HCC. In adjacent tissues, however, high expression of MIP was detected in the nucleus in addition to the cytoplasm. The prepared polyclonal antibody against MIP provides a useful tool for further research on the functions of MIP
Learning Instrumental Variable from Data Fusion for Treatment Effect Estimation
The advent of the big data era brought new opportunities and challenges to draw treatment effect in data fusion, that is, a mixed dataset collected from multiple sources (each source with an independent treatment assignment mechanism). Due to possibly omitted source labels and unmeasured confounders, traditional methods cannot estimate individual treatment assignment probability and infer treatment effect effectively. Therefore, we propose to reconstruct the source label and model it as a Group Instrumental Variable (GIV) to implement IV-based Regression for treatment effect estimation. In this paper, we conceptualize this line of thought and develop a unified framework (Meta-EM) to (1) map the raw data into a representation space to construct Linear Mixed Models for the assigned treatment variable; (2) estimate the distribution differences and model the GIV for the different treatment assignment mechanisms; and (3) adopt an alternating training strategy to iteratively optimize the representations and the joint distribution to model GIV for IV regression. Empirical results demonstrate the advantages of our Meta-EM compared with state-of-the-art methods. The project page with the code and the Supplementary materials is available at https://github.com/causal-machine-learning-lab/meta-em