Cloning and characterization of Sel-1l, a murine homolog of the C. elegans sel-1 gene

The Application of the Tissue Microarray (TMA) Technology to Analyze Cerebral Organoids

"Multi-Omics" technologies have contributed greatly to the understanding of various diseases by enabling researchers to accurately and rapidly investigate the molecular circuitry that connects cellular systems. The tissue-engineered, three-dimensional (3D), in vitro disease model "organoid" integrates the "omics" results in a model system, elucidating the complex links between genotype and phenotype. These 3D structures have been used to model cancer, infectious disease, toxicity, and neurological disorders. Here, we describe the advantage of using the tissue microarray (TMA) technology to analyze human-induced pluripotent stem cell-derived cerebral organoids. Compared with the conventional processing of individual samples, sectioning and staining of TMA slides are faster and can be automated, decreasing labor and reagent costs. The TMA technology faithfully captures cell morphology variations and detects specific biomarkers. The use of this technology can scale up organoid research results in at least two ways: (1) in the number of specimens that can be analyzed simultaneously and (2) in the number of consecutive sections that can be produced for analysis with different probes and antibodies.

SEL1L plays a major role in human malignant gliomas

Suppressor of Lin-12-like (C. elegans) (SEL1L) participates in the endoplasmic reticulum-associated protein degradation pathway, malignant transformation and stem cell biology. We explored the role of SEL1L in 110 adult gliomas, of different molecular subtype and grade, in relation to cell proliferation, stemness, glioma-associated microglia/macrophages (GAMs), prognostic markers and clinical outcome. SEL1L protein expression was assessed by immunohistochemistry and Western blotting. Genetic and epigenetic alterations were detected by molecular genetics techniques. SEL1L was overexpressed in anaplastic gliomas (World Health Organization [WHO] grade III) and in glioblastoma (GB, WHO grade IV) with the highest labelling index (LI) in the latter. Immunoreactivity was significantly associated with histological grade (p = 0.002) and cell proliferation index Ki-67/MIB-1 (p = 0.0001). In GB, SEL1L co-localised with stemness markers Nestin and Sox2. Endothelial cells and vascular pericytes of proliferative tumour blood vessels expressed SEL1L suggesting a role in tumour neo-vasculature. GAMs consistently expressed SEL1L. SEL1L overexpression was significantly associated with TERT promoter mutations (p = 0.0001), EGFR gene amplification (p = 0.0013), LOH on 10q (p = 0.0012) but was mutually exclusive with IDH1/2 mutations (p = 0.0001). SEL1L immunoreactivity correlated with tumour progression and cell proliferation, conditioning poor patient survival and response to therapy. This study emphasises SEL1L as a potential biomarker for the most common subgroup of TERT mutant/EGFR amplified/IDH-WT GBs.

The Expression of Sel1L and Tan-1 in Normal and Neoplastic Cells

We have previously reported on the isolation and chromosomal mapping of a novel human gene (SEL1L), which shows sequence similarity to sel-1, an extragenic suppressor of C. elegans. sel-1 functions as a negative regulator of lin-12 activity, the latter being implicated in the control of diverse cellular differentiation events. In the present study we compare the expression patterns of SEL1L and TAN-1, the human ortholog of lin-12 in normal and neoplastic cells. We found that, whereas both genes are expressed in fetal tissues at similar levels, they are differentially expressed in normal adult and neoplastic cells. In normal adult cells SEL1L is generally present at very low levels; only in the cells of the pancreas does it show maximum expression. By contrast, SEL1L is generally well represented in most neoplastic cells but not in those of pancreatic and gastric carcinomas, where transcription is either downregulated or completely repressed. TAN-1 on the other hand is well represented in almost all normal and neoplastic cells, with very few exceptions. Our observations suggest that SEL1L is presumably implicated in pancreatic and gastric carcinogenesis and that, along with TAN-1, it is very important for normal cell function. Alterations in the expression of SEL1L may be used as a prognostic marker for gastric and pancreatic cancers.

Production of a Monoclonal Antibody Directed against the Recombinant SEL1L Protein

SEL1L, highly similar to the C. elegans sel-1 gene, is a recently cloned human gene whose function is under investigation. SEL1L is differentially expressed in tumors and normal tissues and seems to play a role in tumor growth and aggressiveness. We used the recombinant N-terminus of the SEL1L protein to immunize a Balb/c mouse and produce a monoclonal antibody. A hybridoma secreting an antibody specifically reacting on the SEL1L recombinant fragment was selected. This monoclonal antibody, named MSel1, recognizes the SEL1L protein by Western blotting, immunofluorescence and immunohistochemistry on normal and tumor cells. MSel1 is able to recognize SEL1L even on archival tumor specimens and is therefore particularly appropriate to study SEL1L involvement in tumor progression.

Sel1l knockdown negatively influences zebrafish embryos endothelium

SEL1L (suppressor/enhancer of Lin-12-like) is a highly conserved gene associated with the endoplasmic reticulum-associated degradation (ERAD) pathway and involved in mediating the balance between stem cells self-renewal and differentiation of neural progenitors. It has been recently shown that SEL1L KO mice are embryonic lethal and display altered organogenesis. To better characterize the function of SEL1L in the early stages of embryonic development, we turned to the zebrafish model (Danio rerio). After exploring sel1l expression by RT-PCR and in situ hybridization, we employed a morpholino-mediated down-regulation approach. Results showed extensive impairments in the vasculature, which supports the mice knock-out findings.

mSEL-1L deficiency affects vasculogenesis and neural stem cell lineage commitment

mSEL-1L is a highly conserved ER-resident type I protein, involved in the degradation of misfolded peptides through the ubiquitin-proteasome system (UPS), a pathway known to control the plasticity of the vascular smooth muscle cells (VSMC) phenotype and survival. In this article, we demonstrate that mSEL-1L deficiency interferes with the murine embryonic vascular network, showing particular irregularities in the intracranic and intersomitic neurovascular units and in the cerebral capillary microcirculation. During murine embryogenesis, mSEL-1L is expressed in cerebral areas known to harbor progenitor neural cells, while in the adult brain the protein is specifically restricted to the stem cell niches, co-localizing with Sox2 and Nestin. Null mice are characterized by important defects in the development of telenchephalic regions, revealing conspicuous aberration in neural stem cell lineage commitment. Moreover, mSEL-1L depletion in vitro and in vivo appears to affect the harmonic differentiation of the NSCs, by negatively influencing the corticogenesis processes. Overall, the data presented suggests that the drastic phenotypic characteristics exhibited in mSEL-1L null mice can, in part, be explained by the negative influence it plays on Notch1 signaling pathway.

Pancreas lineage allocation and specification are regulated by sphingosine-1-phosphate signalling

During development, progenitor expansion, lineage allocation, and implementation of differentiation programs need to be tightly coordinated so that different cell types are generated in the correct numbers for appropriate tissue size and function. Pancreatic dysfunction results in some of the most debilitating and fatal diseases, including pancreatic cancer and diabetes. Several transcription factors regulating pancreas lineage specification have been identified, and Notch signalling has been implicated in lineage allocation, but it remains unclear how these processes are coordinated. Using a combination of genetic approaches, organotypic cultures of embryonic pancreata, and genomics, we found that sphingosine-1-phosphate (S1p), signalling through the G protein coupled receptor (GPCR) S1pr2, plays a key role in pancreas development linking lineage allocation and specification. S1pr2 signalling promotes progenitor survival as well as acinar and endocrine specification. S1pr2-mediated stabilisation of the yes-associated protein (YAP) is essential for endocrine specification, thus linking a regulator of progenitor growth with specification. YAP stabilisation and endocrine cell specification rely on Gαi subunits, revealing an unexpected specificity of selected GPCR intracellular signalling components. Finally, we found that S1pr2 signalling posttranscriptionally attenuates Notch signalling levels, thus regulating lineage allocation. Both S1pr2-mediated YAP stabilisation and Notch attenuation are necessary for the specification of the endocrine lineage. These findings identify S1p signalling as a novel key pathway coordinating cell survival, lineage allocation, and specification and linking these processes by regulating YAP levels and Notch signalling. Understanding lineage allocation and specification in the pancreas will shed light in the origins of pancreatic diseases and may suggest novel therapeutic approaches.

A SEL1L mutation links a canine progressive early-onset cerebellar ataxia to the endoplasmic reticulum-associated protein degradation (ERAD) machinery

Inherited ataxias are characterized by degeneration of the cerebellar structures, which results in progressive motor incoordination. Hereditary ataxias occur in many species, including humans and dogs. Several mutations have been found in humans, but the genetic background has remained elusive in dogs. The Finnish Hound suffers from an early-onset progressive cerebellar ataxia. We have performed clinical, pathological, and genetic studies to describe the disease phenotype and to identify its genetic cause. Neurological examinations on ten affected dogs revealed rapidly progressing generalized cerebellar ataxia, tremors, and failure to thrive. Clinical signs were present by the age of 3 months, and cerebellar shrinkage was detectable through MRI. Pathological and histological examinations indicated cerebellum-restricted neurodegeneration. Marked loss of Purkinje cells was detected in the cerebellar cortex with secondary changes in other cortical layers. A genome-wide association study in a cohort of 31 dogs mapped the ataxia gene to a 1.5 Mb locus on canine chromosome 8 (p_raw = 1.1×10⁻⁷, p_genome = 7.5×10⁻⁴). Sequencing of a functional candidate gene, sel-1 suppressor of lin-12-like (SEL1L), revealed a homozygous missense mutation, c.1972T>C; p.Ser658Pro, in a highly conserved protein domain. The mutation segregated fully in the recessive pedigree, and a 10% carrier frequency was indicated in a population cohort. SEL1L is a component of the endoplasmic reticulum (ER)–associated protein degradation (ERAD) machinery and has not been previously associated to inherited ataxias. Dysfunctional protein degradation is known to cause ER stress, and we found a significant increase in expression of nine ER stress responsive genes in the cerebellar cortex of affected dogs, supporting the pathogenicity of the mutation. Our study describes the first early-onset neurodegenerative ataxia mutation in dogs, establishes an ERAD–mediated neurodegenerative disease model, and proposes SEL1L as a new candidate gene in progressive childhood ataxias. Furthermore, our results have enabled the development of a genetic test for breeders.

Hereditary ataxias are a heterogeneous group of rare disorders characterized by progressive cerebellar neurodegeneration. Several causative mutations have been identified in various forms of human ataxias. In addition to humans, inherited ataxias have been described in several other species, including the domestic dog. In this study, we have studied the clinical and genetic properties of cerebellar ataxia in the Finnish Hound dog breed. The breed suffers from a progressive ataxia that has an early onset before the age of 3 months. Affected puppies have difficulties in coordinating their movements and balance, and have to be euthanized due to rapidly worsening symptoms. Our pedigree analysis suggested an autosomal recessive mode of inheritance, which was confirmed by identifying a homozygous mutation in the SEL1L gene through genome-wide association and linkage analyses. The SEL1L protein functions in a protein quality control pathway that targets misfolded proteins to degradation in the endoplasmic reticulum. Mutations in the SEL1L gene have not been previously found in ataxias. Our study indicates SEL1L as a novel candidate gene for human childhood ataxias, establishes a large animal model to investigate mechanisms of cerebellar neurodegeneration, and enables carrier screening for breeding purposes.

Haploid insufficiency of suppressor enhancer Lin12 1-like (SEL1L) protein predisposes mice to high fat diet-induced hyperglycemia

Increasing evidence suggests that endoplasmic reticulum (ER) stress plays an important role in the pathogenesis of type 2 diabetes mellitus. SEL1L is an ER membrane protein that is highly expressed in the pancreatic islet and acinar cells. We have recently reported that a deficiency of SEL1L causes systemic ER stress and leads to embryonic lethality in mice. Here we show that mice with one functional allele of Sel1l (Sel1l(+/-)) are more susceptible to high fat diet (HFD)-induced hyperglycemia. Sel1l(+/-) mice have a markedly reduced β-cell mass as a result of decreased β-cell proliferation. Consequently, Sel1l(+/-) mice are severely glucose-intolerant and exhibit significantly retarded glucose-stimulated insulin secretion. Pancreatic islets from Sel1l(+/-) mice stimulated with a high concentration of glucose in vitro express significantly higher levels of unfolded protein response genes than those from wild-type control mice. Furthermore, dominant-negative interference of SEL1L function in insulinoma cell lines severely impairs, whereas overexpression of SEL1L efficiently improves protein secretion. Taken together, our results indicate that haploid insufficiency of SEL1L predispose mice to high fat diet-induced hyperglycemia. Our findings highlight a critical and previously unknown function for SEL1L in regulating adult β-cell function and growth.

mSEL-1L (Suppressor/enhancer Lin12-like) protein levels influence murine neural stem cell self-renewal and lineage commitment

Murine SEL-1L (mSEL-1L) is a key component of the endoplasmic reticulum-associated degradation pathway. It is essential during development as revealed by the multi-organ dysfunction and in uterus lethality occurring in homozygous mSEL-1L-deficient mice. Here we show that mSEL-1L is highly expressed in pluripotent embryonic stem cells and multipotent neural stem cells (NSCs) but silenced in all mature neural derivatives (i.e. astrocytes, oligodendrocytes, and neurons) by mmu-miR-183. NSCs derived from homozygous mSEL-1L-deficient embryos (mSEL-1L(-/-) NSCs) fail to proliferate in vitro, show a drastic reduction of the Notch effector HES-5, and reveal a significant down-modulation of the early neural progenitor markers PAX-6 and OLIG-2, when compared with the wild type (mSEL-1L(+/+) NSCs) counterpart. Furthermore, these cells are almost completely deprived of the neural marker Nestin, display a significant decrease of SOX-2 expression, and rapidly undergo premature astrocytic commitment and apoptosis. The data suggest severe self-renewal defects occurring in these cells probably mediated by misregulation of the Notch signaling. The results reported here denote mSEL-1L as a primitive marker with a possible involvement in the regulation of neural progenitor stemness maintenance and lineage determination.

A migration signature and plasma biomarker panel for pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma is a disease of extremely poor prognosis for which there are no reliable markers of asymptomatic disease. To identify pancreatic cancer biomarkers, we focused on a genomic interval proximal to the most common fragile site in the human genome, chromosome 3p12, which undergoes smoking-related breakage, loss of heterozygosity, and homozygous deletion as an early event in many epithelial tumors, including pancreatic cancers. Using a functional genomic approach, we identified a seven-gene panel (TNC, TFPI, TGFBI, SEL-1L, L1CAM, WWTR1, and CDC42BPA) that was differentially expressed across three different expression platforms, including pancreatic tumor/normal samples. In addition, Ingenuity Pathways Analysis (IPA) and literature searches indicated that this seven-gene panel functions in one network associated with cellular movement/morphology/development, indicative of a "migration signature" of the 3p pathway. We tested whether two secreted proteins from this panel, tenascin C (TNC) and tissue factor pathway inhibitor (TFPI), could serve as plasma biomarkers. Plasma ELISA assays for TFPI/TNC resulted in a combined area under the curve (AUC) of 0.88 and, with addition of CA19-9, a combined AUC for the three-gene panel (TNC/TFPI/CA19-9), of 0.99 with 100% specificity at 90% sensitivity and 97.22% sensitivity at 90% specificity. Validation studies using TFPI only in a blinded sample set increased the performance of CA19-9 from an AUC of 0.84 to 0.94 with the two-gene panel. Results identify a novel 3p pathway-associated migration signature and plasma biomarker panel that has utility for discrimination of pancreatic cancer from normal controls and promise for clinical application.

Deficiency of suppressor enhancer Lin12 1 like (SEL1L) in mice leads to systemic endoplasmic reticulum stress and embryonic lethality

Stress in the endoplasmic reticulum (ER) plays an important causal role in the pathogenesis of several chronic diseases such as Alzheimer, Parkinson, and diabetes mellitus. Insight into the genetic determinants responsible for ER homeostasis will greatly facilitate the development of therapeutic strategies for the treatment of these debilitating diseases. Suppressor enhancer Lin12 1 like (SEL1L) is an ER membrane protein and was thought to be involved in the quality control of secreted proteins. Here we show that the mice homozygous mutant for SEL1L were embryonic lethal. Electron microscopy studies revealed a severely dilated ER in the fetal liver of mutant embryos, indicative of alteration in ER homeostasis. Consistent with this, several ER stress responsive genes were significantly up-regulated in the mutant embryos. Mouse embryonic fibroblast cells deficient in SEL1L exhibited activated unfolded protein response at the basal state, impaired ER-associated protein degradation, and reduced protein secretion. Furthermore, markedly increased apoptosis was observed in the forebrain and dorsal root ganglions of mutant embryos. Taken together, our results demonstrate an essential role for SEL1L in protein quality control during mouse embryonic development.

SEL1L deficiency impairs growth and differentiation of pancreatic epithelial cells

Background

The vertebrate pancreas contains islet, acinar and ductal cells. These cells derive from a transient pool of multipotent pancreatic progenitors during embryonic development. Insight into the genetic determinants regulating pancreatic organogenesis will help the development of cell-based therapies for the treatment of diabetes mellitus. Suppressor enhancer lin12/Notch 1 like (Sel1l) encodes a cytoplasmic protein that is highly expressed in the developing mouse pancreas. However, the morphological and molecular events regulated by Sel1l remain elusive.

Results

We have characterized the pancreatic phenotype of mice carrying a gene trap mutation in Sel1l. We show that Sel1l expression in the developing pancreas coincides with differentiation of the endocrine and exocrine lineages. Mice homozygous for the gene trap mutation die prenatally and display an impaired pancreatic epithelial morphology and cell differentiation. The pancreatic epithelial cells of Sel1l mutant embryos are confined to the progenitor cell state throughout the secondary transition. Pharmacological inhibition of Notch signaling partially rescues the pancreatic phenotype of Sel1l mutant embryos.

Conclusions

Together, these data suggest that Sel1l is essential for the growth and differentiation of endoderm-derived pancreatic epithelial cells during mouse embryonic development.

SEL1L a multifaceted protein playing a role in tumor progression

Since the cloning in 1997 of SEL1L, the human ortholog of the sel-1 gene of C. elegans, most studies have focused on its role in cancer progression and have provided significant evidences to link its increased expression to a decrease in tumor aggressiveness. SEL1L resides on a "Genome Desert area" on chromosome 14q24.3-31 and is highly conserved in evolution. The function of the SEL1L encoded protein is still very elusive although, several evidences from lower organisms indicate that it plays a major role in protein degradation using the ubiquitin-proteosome system. SEL1L has a very complex structure made up of modules: genomically it consists of 21 exons featuring several alternative transcripts encoding for putative protein isoforms. This structural complexity ensures protein flexibility and specificity, indeed the protein was found in different sub-cellular compartments and may turn on a particular transcript in response to specific stimuli. The overall architecture of SEL1L guarantees an exquisite regulation in the expression of the gene.

SEL1L expression in non-small cell lung cancer

SEL1L gene product plays a role in cell transformation and tumor progression in human breast, pancreas, esophageal, and prostate cancer. SEL1L expression was evaluated in a series of 76 surgically resected non-small cell lung carcinomas to investigate its clinical significance. SEL1L is scarcely detectable in normal lung, whereas in the initial stages of cell transformation, it becomes consistently expressed with evident staining in bronchial squamous metaplasia and in associated dysplastic changes. SEL1L immunoreactivity can be detected both in the cytoplasm and less commonly in the nuclei; the subcellular location correlates with tumor histotype, with cytoplasmic immunoreactivity being most prevalent in squamous cell carcinomas (P = .0005) and nuclear immunoreactivity being associated with adenocarcinomas (P = .02). Nuclear import and export signals are present in the SEL1L coding sequence, justifying the different subcellular location of the protein. SEL1L immunoreactivity was inversely correlated with tumor grade (P = .05); when considering only the adenocarcinomas, a stronger association was found (P = .006). SEL1L messenger RNA and protein evaluation in lung cancer cell lines confirmed the expression of the gene and the dual subcellular location of the protein in lung tumors. The data here reported suggest that, in non-small cell lung carcinoma, SEL1L may be an indicator of cell transformation, thus having important biologic and clinical implications.

Gene expression in response to endoplasmic reticulum stress in Arabidopsis thaliana

Eukaryotic cells respond to the accumulation of unfolded proteins in the endoplasmic reticulum (ER). In this case, so-called unfolded protein response (UPR) genes are induced. We determined the transcriptional expression of Arabidopsis thaliana UPR genes by fluid microarray analysis of tunicamycin-treated plantlets. Two hundred and fifteen up-regulated genes and 17 down-regulated ones were identified. These genes were reanalyzed with functional DNA microarrays, using DNA fragments cloned through fluid microarray analysis. Finally, 36 up-regulated and two down-regulated genes were recognized as UPR genes. Among them, the up-regulation of genes related to protein degradation (HRD1, SEL-1L/HRD3 and DER1), regulation of translation (P58(IPK)), and apoptosis (BAX inhibitor-1) was reconfirmed by real-time reverse transcriptase-PCR. The induction of SEL-1L protein in an Arabidopsis membrane fraction on tunicamycin-treatment was demonstrated. Phosphorylation of initiation factor-2alpha, which was inhibited by P58(IPK), was decreased in tunicamycin-treated plantlets. However, regulatory changes in translation caused by ER stress were not detected in Arabidopsis. Plant cells appeared to have a strategy for overcoming ER stress through enhancement of protein folding activity, degradation of unfolded proteins, and regulation of apoptosis, but not regulation of translation.

SEL1L and squamous cell carcinoma of the esophagus

The gene SEL1L is involved both in human breast and pancreatic cancer progression. It is located on 14q24.3-31, a region known to be lost in invasive cancer of the esophagus. We aimed to assess whether SEL1L could become a useful biomarker for this cancer. We assessed SEL1L mRNA and protein expression in 35 patients and found it to be weak in low-grade and strong in high-grade dysplasia. Although the majority of cancer patients showed differential expression (mRNA and protein) of SEL1L, in five cases it was completely absent; these patients had the worst outcomes. SEL1L immunoreactivity was negative in normal tissue samples from five patients with mild esophagitis as well as in normal mucosa adjacent to the tumor. We hypothesize that SEL1L could influence those cellular changes that mediate the transition from a normal mucosa to a neoplastic lesion and may help in the identification of those patients at higher risk of developing this cancer. The specific impact of SEL1L in esophageal cancer needs further investigation.

Identification of a novel polymorphism in the fibronectin type II domain of the SEL1L gene and possible relation to the persistent hyperinsulinemic hypoglycemia of infancy

SEL1L, a human gene located on chromosome 14q24.3-q31, is highly expressed in adult pancreas. It is proximal to D14S67 (IDDM11) a proposed type I diabetes susceptibility locus. Considering the organ specific expression of SEL1L, a fundamental role of SEL1L in pancreatic growth can be hypothesized. While screening for mutations in young diabetic patients, in children affected by persistent hyperinsulinemic hypoglycemia of infancy (PHHI), in patients with non-functional endocrine tumours and in over 100 control subjects, we identified a novel polymorphism (D162G) residing on the fourth exon of the gene. This exon encodes for the fibronectin type II domain and the nucleotide change involves a highly conserved amino acid. The D162G polymorphism induces a major change in the amino acid composition producing a possible disruptive role in collagen binding.

RNA-mediated interference indicates that SEL1L plays a role in pancreatic beta-cell growth

The specificity of SEL1L expression and promoter activity for the pancreatic cell population, its chromosomal location, as well as its similarities to the yeast Hrd3p protein, a component of HRD complex which is responsible for endoplasmic reticulum (ER)-associated degradation of numerous ER-resident proteins, prompted us to study its effects on beta cell function. In this study we show that lowering SEL1L expression, by using the short interfering RNAs technology as well as antisense transfection, resulted in severe perturbation of betaTC-3 growth and metabolic activity. We hypothesize that SEL1L may exert its function by protecting the cells from ER stress and could counteract immune responses.

SEL1L expression in pancreatic adenocarcinoma parallels SMAD4 expression and delays tumor growth in vitro and in vivo

Recent data suggest that SEL1L may play an important role in pancreatic carcinoma, similar to breast cancer, where the expression of SEL1L has been associated with a reduction in both proliferative activity in vitro and clinical tumor aggressiveness. To investigate this possibility, we examined the expression of Sel1L in a series of primary pancreatic carcinomas by immunohistochemistry and characterized the effects of Sel1L overexpression both in vitro and in vivo. In 74 pancreatic cancers analysed, 36% lacked Sel1L expression, although there was no significant correlation between the expression of Sel1L and any clinicopathologic parameter, including survival. However, immunohistochemical reactivity for Sel1L and Dpc4/Smad4 was concordant in 69% of cases (chi(2) test P&<0.004). Overexpression of SEL1L in stably transfected pancreatic cancer cells caused both a decrease in clonogenicity and anchorage-independent growth as well as a significant increase in the levels of activin A and SMAD4. When implanted in nude mice, Suit-2-SEL1L-overexpressing clones displayed a considerably reduced rate of tumor growth. Thus, it can be hypothesized that Sel1L plays an important function in the growth and aggressiveness of pancreatic carcinoma. Moreover, our data provide evidence that SEL1L has an impact on the expression of genes involved in regulation of cellular growth, possibly through the TGF-beta signaling pathway.

Identification of genetic pathways activated by the androgen receptor during the induction of proliferation in the ventral prostate gland

The androgen receptor (AR), when complexed with 5alpha-dihydrotestosterone (DHT), supports the survival and proliferation of prostate cells, a process critical for normal development, benign prostatic hypertrophy, and tumorigenesis. However, the androgen-responsive genetic pathways that control prostate cell division and differentiation are largely unknown. To identify such pathways, we examined gene expression in the ventral prostate 6 and 24 h after DHT administration to androgen-depleted rats. 234 transcripts were expressed significantly differently from controls (p < 0.05) at both time points and were subjected to extensive data mining. Functional clustering of the data reveals that the majority of these genes can be classified as participating in induction of secretory activity, metabolic activation, and intracellular signaling/signal transduction, indicating that AR rapidly modulates the expression of genes involved in proliferation and differentiation in the prostate. Notably AR represses the expression of several key cell cycle inhibitors, while modulating members of the wnt and notch signaling pathways, multiple growth factors, and peptide hormone signaling systems, and genes involved in MAP kinase and calcium signaling. Analysis of these data also suggested that p53 activity is negatively regulated by AR activation even though p53 RNA was unchanged. Experiments in LNCaP prostate cancer cells reveal that AR inhibits p53 protein accumulation in the nucleus, providing a post-transcriptional mechanism by which androgens control prostate cell growth and survival. In summary these data provide a comprehensive view of the earliest events in AR-mediated prostate cell proliferation in vivo, and suggest that nuclear exclusion of p53 is a critical step in prostate growth.

Fgf10maintains notch activation, stimulates proliferation, and blocks differentiation of pancreatic epithelial cells

The pancreas is an endodermally derived organ that initially appears as a dorsal and ventral protrusion of the primitive gut epithelium. The pancreatic progenitor cells present in these early pancreatic anlagen proliferate and eventually give rise to all pancreatic cell types. The fibroblast growth factor receptor (FGFR) 2b high-affinity ligand FGF10 has been linked to pancreatic epithelial cell proliferation, and we have shown previously that Notch signalling controls pancreatic cell differentiation by means of lateral inhibition. In the developing pancreas, activated intracellular Notch appears to be required for maintaining cells in the progenitor state, in part by blocking the expression of the pro-endocrine gene neurogenin 3 (ngn3), and hence endocrine cell differentiation. Here, we show that persistent expression of Fgf10 in the embryonic pancreas of transgenic mice also inhibits pancreatic cell differentiation, while stimulating pancreatic epithelial cell proliferation. We provide evidence that one of the effects of the persistent expression of Fgf10 in the developing pancreas is maintained Notch activation, which results in impaired expression of ngn3 within the pancreatic epithelium. Together, our data suggest a role for FGF10/FGFR2b signalling in regulation of pancreatic cell proliferation and differentiation and that FGF10/FGFR2b signalling affects the Notch-mediated lateral inhibition pathway.

Genetic modifiers of the age at diagnosis of diabetes (MODY3) in carriers of hepatocyte nuclear factor-1alpha mutations map to chromosomes 5p15, 9q22, and 14q24

Mutations in hepatocyte nuclear factor (HNF)-1alpha (MODY3) account for the largest proportion of maturity-onset diabetes of the young (MODY) cases in the U.S. This form of diabetes is characterized by impaired insulin secretion in response to glucose, but wide variability exists in the severity of hyperglycemia and in the age at which it becomes clinically manifest. We have previously shown that the age at onset of diabetes in MODY3 families is influenced by familial factors (including modifying genes) and exposure to diabetes in utero. To identify genes influencing the onset of MODY3, we conducted a genome scan in 13 extended MODY families in which diabetes segregates with an HNF-1alpha mutation. Linkage with age at onset of diabetes was assessed by genetic variance component analysis using SOLAR. The locus with the strongest evidence of linkage was on chromosome 14q24 (D14S588; logarithm of odds [LOD] = 2.58, P = 0.0004). This location overlaps with IDDM11 and includes SEL1L, a negative regulator of the Notch pathway that may control islet development. Linkage evidence also supported loci on 5p15 (D5S817; LOD = 2.44, P = 0.0004) and 9q22 (D9S910; LOD = 2.02, P = 0.0018). The latter matches a region linked to 2-h insulin levels in Pima Indians. Less strong linkage evidence was observed at three other regions: chromosomes 3p24 (LOD = 1.44), 7q21 (1.20), and 16q23 (1.51). Our data are consistent with the existence of multiple loci that contribute to the expression of the MODY3 phenotype. Identification of these genes will offer new insights into the pathophysiology of MODY that may, in turn, increase our understanding of the cellular events underlying more common forms of diabetes.

Notch mediates TGF alpha-induced changes in epithelial differentiation during pancreatic tumorigenesis

Notch signaling regulates cell fate decisions in a wide variety of adult and embryonic tissues. Here we show that Notch pathway components and Notch target genes are upregulated in invasive pancreatic cancer, as well as in pancreatic cancer precursors from both mouse and human. In mouse pancreas, ectopic Notch activation results in accumulation of nestin-positive precursor cells and expansion of metaplastic ductal epithelium, previously identified as a precursor lesion for pancreatic cancer. Notch is also activated as a direct consequence of EGF receptor activation in exocrine pancreas and is required for TGF alpha-induced changes in epithelial differentiation. These findings suggest that Notch mediates the tumor-initiating effects of TG alpha by expanding a population of undifferentiated precursor cells.

Proteolysis and sterol regulation

The mammalian cell continuously adjusts its sterol content by regulating levels of key sterol synthetic enzymes and levels of LDL receptors that mediate uptake of cholesterol-laden particles. Control is brought about by sterol-regulated transcription of relevant genes and by regulated degradation of the committed step enzyme HMG-CoA reductase (HMGR). Current work has revealed that proteolysis is at the heart of each of these mechanistically distinct axes. Transcriptional control is effected by regulated cleavage of the membrane-bound transcription factor sterol regulatory element binding protein (SREBP), and HMGR degradation is brought about by ubiquitin-mediated degradation. In each case, ongoing cell biological processes are being harnessed to bring about regulation. The secretory pathway plays a central role in allowing sterol-mediated control of transcription. The constitutively active endoplasmic reticulum (ER) quality control apparatus is employed to bring about regulated destruction of HMGR. This review describes the methods and results of various studies to understand the mechanisms and molecules involved in these distinct but interrelated aspects of sterol regulation and the intriguing similarities that appear to exist at the levels of protein sequence and cell biology.

Cross-species conservation of SEL1L, a human pancreas-specific expressing gene

SEL1L is a recently cloned and organ-specific expressing human gene whose function is still at an embryonic stage but displays several interesting characteristics, among which a remarkable cross-species conservation. During evolution, the gene structural complexity increased, suggesting a diversification of its function; however, several amino acid motifs remain perfectly conserved from the bacteria to the human protein. SEL1L is the human ortholog of the C. elegans gene sel-1; the latter is implicated in the negative regulation of LIN-12/GLP-1/Notch receptor proteins. These receptor proteins play fundamental roles in signal transduction pathways and are key players in cell fate determination during the development of various organs. Studies in model organisms, such as C. elegans, helped to illuminate fundamental mechanisms involved in normal cellular functions and human diseases. This paper describes the conserved nature of SEL1L across a wide range of species suggesting, that the encoded protein most likely exerts a very important biological function; it may belong to a subclass of genes considered to be "essential."

ER-associated degradation in protein quality control and cellular regulation

The ER-associated degradation (ERAD) pathway directs ubiquitin-mediated degradation of a variety of ER-associated misfolded and normal proteins. Recent studies have delineated the molecular machinery responsible for protein ubiquitination and highlighted mechanistic questions surrounding the recognition, extraction and proteasomal destruction of the diverse array of ERAD substrates. Consideration of separate lines of work on this versatile pathway now indicate that despite its central role as an avenue of cellular quality control, ERAD is also harnessed for feedback regulation of sterol synthesis, and most likely numerous other cellular processes. These studies give ERAD a larger role in cellular function, and imply that cellular quality-control pathways could be widely employed in both natural and pharmaceutical control of individual proteins.

Genetics of type 1 diabetes mellitus

At least 20 different chromosomal regions have been linked to type 1 diabetes (T1D) susceptibility in humans, using genome screening, candidate gene testing, and studies of human homologues of mouse susceptibility genes. The largest contribution from a single locus (IDDM1) comes from several genes located in the MHC complex on chromosome 6p21.3, accounting for at least 40% of the familial aggregation of this disease. Approximately 30% of T1D patients are heterozygous for HLA-DQA1*0501-DQB1*0201/DQA1*0301-DQB1*0302 alleles (formerly referred to as HLA-DR3/4 and for simplification usually shortened to HLA-DQ2/DQ8), and a particular HLA-DQ6 molecule (HLA-DQA1*0102-DQB1*0602) is associated with dominant protection from the disease. There is evidence that certain residues important for structure and function of both HLA-DQ and DR peptide-binding pockets determine disease susceptibility and resistance. Independent confirmation of the IDDM2 locus on chromosome 11p15.5 has been achieved in both case-control and family-based studies, whereas associations with the other potential IDDM loci have not always been replicated. Several possibilities to explain these variable results from different studies are discussed, and a key factor affecting both linkage and association studies is that the genetic basis of T1D susceptibility may differ between ethnic groups. Some future strategies to address these problems are proposed. These include increasing the sample size in homogenous ethnic groups, high throughput genotyping and genomewide linkage disequilibrium (LD) mapping to establish disease associated ancestral haplotypes. Elucidation of the function of particular genes ('functional genomics') in the pathogenesis of T1D will be a most important element in future studies in this field, in addition to more sophisticated methods of statistical analyses.

Allele frequency of two intragenic microsatellite loci of SEL1L gene in Northern Italian population

Two cytosine-adenine (CA) repeats CAR/CAL and RepIN20 occur in the human SEL1L gene, which is regarded as a candidate gene for insulin-dependent diabetes mellitus (IDDM) and Grave's disease. We have characterized these repeats to determine if they might serve as effective microsatellite markers for linkage analysis to clarify whether SEL1L gene plays a role in the pathogenesis of these autoimmune diseases. The allele frequencies and average heterozygosity of the microsatellite repeats were analysed in 94 DNA samples from peripheral blood mononuclear (PBMC) cells from adults of Northern Italy. The average heterozygosity was 0.68 for CAR/CAL polymorphism and 0.85 for RepIN20. The size of PCR fragments of CAR/CAL ranged from 207-225 bp and the most frequent allele was 207 bp (40.4%). The size of the fragments of RepIN20 ranged from 237-255 bp and the most frequent allele was 249 bp (30.8%). In the light of the highly polymorphic nature of both microsatellites and their intragenic location in SEL1L gene, we suggest that they could provide a means for linkage analysis to clarify the potential role of SEL1L in conferring susceptibility to IDDM or Grave's disease.

Allelic polymorphisms in the transcriptional regulatory region of human SEL1L

In this work, we explored the existence of genetic variants within the SEL1L transcriptional regulatory region by direct sequencing of the basal promoter. SEL1L is the human ortholog of the Caenorhabditis elegans gene sel-1, a negative regulator of LIN-12/NOTCH receptor proteins. To understand the relation in SEL1L transcription pattern observed in different epithelial cells, we analysed its promoter activity. We found it to be considerably higher only in pancreatic cells. We then looked for the presence of genetic variability within this region by sequencing the minimal promoter of 63 individuals (126 alleles); two new and associated polymorphic variants were found only in few lung carcinoma bearing patients. The functional effects of this polymorphism was analysed by transient transfection assay which resulted in a significant increase in the transcriptional activity of the gene.

No evidence for SEL1L as a candidate gene for IDDM11-conferred susceptibility

BACKGROUND

The SEL1L gene is located on human chromosome 14q24.3-31 close to D14S67 which has been previously proposed to be a type 1 diabetes mellitus locus (IDDM11). Sel-1 is a negative regulator of the Notch signalling pathway and SEL1L is selectively expressed in adult pancreas and islets of Langerhans. This suggests that SEL1L may be a candidate gene for IDDM11.

METHODS

We have analysed two newly identified CA-repeat polymorphisms within the genomic sequence of the SEL1L locus for association with type 1 diabetes mellitus (T1DM) in 152 Danish T1DM-affected sib-pair families and in 240 Sardinian families (229 simplex and 11 sib-pair families).

RESULTS

No evidence for association of the two SEL1L markers with T1DM was observed in either the Danish or the Sardinian families. We have also used allelic sharing methods to analyse linkage with T1DM in the IDDM11 region using the same markers and the Danish collection of affected sib-pair families. No evidence of linkage was observed (Z(max)=0.86).

CONCLUSION

Although several lines of evidence suggest that SEL1L might be a candidate for IDDM11-conferred susceptibility to T1DM the present study does not support this hypothesis.

Activin A induces expression of rat Sel-1l mRNA, a negative regulator of notch signaling, in rat salivary gland-derived epithelial cells

We previously established a rat submandibular gland (SMG)-derived epithelial cell line (RSMG-1) to study the mechanism of morphogenesis in salivary gland development and regeneration. We found that activin A regulated the branching morphogenesis of RSMG-1 cells, suggesting that it is involved in SMG morphogenesis. We used a subtraction cloning procedure with activin-A-treated and untreated RSMG-1 cells to identify activin-A-induced genes. One of the genes detected encoded a rat homologue of Sel-1l (rSel-1l). rSel-1l is a mammalian homologue of C. elegans sel-1, which is a negative regulator of Notch signaling. In this study, we confirmed that activin A induces rSel-1l mRNA expression in RSMG-1 cells, and that rSel-1l is expressed in SMG acinar cells. These results suggest that activin A regulates the differentiation of RSMG-1 cells to acinar cells.

SEL1L microsatellite polymorphism in Japanese patients with autoimmune thyroid diseases

The autoimmune thyroid diseases (AITDs), comprising Graves' disease (GD) and Hashimoto's thyroiditis (HT), appear to develop as a result of complex interactions between predisposing genes and environmental triggers. A recently performed genome-wide linkage study identified six loci that showed evidence for linkage to AITD. One locus, GD-1, on chromosome 14q31 was mapped to within 2 centimorgans (cM) of the recently reported multinodular goiter (MNG)-1 locus. Furthermore, microsatellite markers for the thyroid stimulating hormone receptor gene on chromosome 14q31 were associated with AITDs in the Japanese population. A newly isolated growth factor, SEL1L, was recently mapped to 14q31, and we considered it an interesting candidate gene to examine with respect to both GD and MNG. We therefore have analyzed a dinucleotide (CA)n repeat polymorphism in the intron 20 of the SEL1L gene in patients with AITDs and in normal subjects. The polymorphic marker was analyzed by polymerase chain reaction (PCR) followed by electrophoresis on denaturing polyacrylamide gels. There was no significant difference in the distributions of SEL1L alleles between patients and controls. The present results do not support an association between a dinucleotide repeat polymorphism in intron 20 of the SEL1L gene and AITD in Japanese women.

Cloning and functional analysis of SEL1L promoter region, a pancreas-specific gene

We examined the promoter activity of SEL1L, the human ortholog of the C. elegans gene sel-1, a negative regulator of LIN-12/NOTCH receptor proteins. To understand the relation in SEL1L transcription pattern observed in different epithelial cells, we determined the transcription start site and sequenced the 5' flanking region. Sequence analysis revealed the presence of consensus promoter elements--GC boxes and a CAAT box--but the absence of a TATA motif. Potential binding sites for transcription factors that are involved in tissue-specific gene expression were identified, including: activator protein-2 (AP-2), hepatocyte nuclear factor-3 (HNF3 beta), homeobox Nkx2-5 and GATA-1. Transcription activity of the TATA-less SEL1L promoter was analyzed by transient transfection using luciferase reporter gene constructs. A core basal promoter of 302 bp was sufficient for constitutive promoter activity in all the cell types studied. This genomic fragment contains a CAAT and several GC boxes. The activity of the SEL1L promoter was considerably higher in mouse pancreatic beta cells (beta TC3) than in several human pancreatic neoplastic cell lines; an even greater reduction of its activity was observed in cells of nonpancreatic origin. These results suggest that SEL1L promoter may be a useful tool in gene therapy applications for pancreatic pathologies.

Endoplasmic reticulum degradation requires lumen to cytosol signaling. Transmembrane control of Hrd1p by Hrd3p

Endoplasmic reticulum (ER)-associated degradation (ERAD) is required for ubiquitin-mediated destruction of numerous proteins. ERAD occurs by processes on both sides of the ER membrane, including lumenal substrate scanning and cytosolic destruction by the proteasome. The ER resident membrane proteins Hrd1p and Hrd3p play central roles in ERAD. We show that these two proteins directly interact through the Hrd1p transmembrane domain, allowing Hrd1p stability by Hrd3p-dependent control of the Hrd1p RING-H2 domain activity. Rigorous reevaluation of Hrd1p topology demonstrated that the Hrd1p RING-H2 domain is located and functions in the cytosol. An engineered, completely lumenal, truncated version of Hrd3p functioned normally in both ERAD and Hrd1p stabilization, indicating that the lumenal domain of Hrd3p regulates the cytosolic Hrd1p RING-H2 domain by signaling through the Hrd1p transmembrane domain. Additionally, we identified a lumenal region of Hrd3p dispensable for regulation of Hrd1p stability, but absolutely required for normal ERAD. Our studies show that Hrd1p and Hrd3p form a stoichiometric complex with ERAD determinants in both the lumen and the cytosol. The HRD complex engages in lumen to cytosol communication required for regulation of Hrd1p stability and the coordination of ERAD events on both sides of the ER membrane.