Lhx2 expression promotes self-renewal of a distinct multipotential hematopoietic progenitor cell in embryonic stem cell-derived embryoid bodies

Functional heterogeneity of immune defenses in molluscan oysters Crassostrea hongkongensis revealed by high-throughput single-cell transcriptome

Oyster is the worldwide aquaculture molluscan and evolves a complex immune defense system, with hemocytes as the major immune system for its host defense. However, the functional heterogeneity of hemocyte has not been characterized, which markedly hinders our understanding of its defense role. Here, we used the single-cell transcriptome profiling (scRNA-seq), which provides a high-resolution visual insight into its dynamics, to map the hemocyte and assess its heterogeneity in a molluscan oyster Crassostrea hongkongensis. By combining with the cell type specific RNA-seq, thirteen subpopulations belonging to granulocyte, semi-granulocyte, and hyalinocyte were revealed. The granulocytes mainly participated in immune response and autophagy process. Pseudo-temporal ordering of granulocytes identified two different cell-lineages. The hematopoietic transcription factors regulated networks controlling their differentiations were also identified. We further identified one subpopulation of granulocytes in immune activate states with the cell cycle and immune responsive genes expressions, which illustrated the functional heterogeneity of the same cell type. Collectively, our scRNA-seq analysis demonstrated the hemocytes diversity of molluscans. The results are important in our understanding of the immune defense evolution and functional differentiation of hemocytes in Phylum Mollusca.

Lymphoblastoid cell line with B1 cell characteristics established from a chronic lymphocytic leukemia clone by in vitro EBV infection

Chronic lymphocytic leukemia (CLL) cells express the receptor for Epstein-Barr virus (EBV) and can be infected in vitro. Infected cells do not express the growth-promoting set of EBV-encoded genes and therefore they do not yield LCLs, in most experiments. With exceptional clones, lines were obtained however. We describe a new line, HG3, established by in vitro EBV-infection from an IGHV1–2 unmutated CLL patient clone. All cells expressed EBNA-2 and LMP-1, the EBV-encoded genes pivotal for transformation. The karyotype, FISH cytogenetics and SNP-array profile of the line and the patient's ex vivo clone showed biallelic 13q14 deletions with genomic loss of DLEU7, miR15a/miR16–1, the two micro-RNAs that are deleted in 50% of CLL cases. Further features of CLL cells were: expression of CD5/CD20/CD27/CD43 and release of IgM natural antibodies reacting with oxLDL-like epitopes on apoptotic cells (cf. stereotyped subset-1). Comparison with two LCLs established from normal B cells showed 32 genes expressed at higher levels (> 2-fold). Among these were LHX2 and LILRA. These genes may play a role in the development of the disease. LHX2 expression was shown in self-renewing multipotent hematopoietic stem cells, and LILRA4 codes for a receptor for bone marrow stromal cell antigen-2 that contributes to B cell development. Twenty-four genes were expressed at lower levels, among these PARD3 that is essential for asymmetric cell division. These genes may contribute to establish precursors of CLL clones by regulation of cellular phenotype in the hematopoietic compartment. Expression of CD5/CD20/CD27/CD43 and spontaneous production of natural antibodies may identify the CLL cell as a self-renewing B1 lymphocyte.

LIM homeobox 2 promotes interaction between human iPS-derived hepatic progenitors and iPS-derived hepatic stellate-like cells

Human induced pluripotent stem (iPS) cells can differentiate into hepatocyte lineages, although the phenotype of the differentiated cells is immature compared to adult hepatocytes. Improvement of cell-cell interactions between epithelium and mesenchyme is a potential approach to address this phenotype issue. In this study, we developed a model system for improving interactions between human iPS-derived hepatic progenitor cells (iPS-HPCs) and human iPS-derived hepatic stellate cell-like cells (iPS-HSCs). The phenotype of iPS-HSCs, including gene and protein expression profiles and vitamin A storage, resembled that of hepatic stellate cells. Direct co-culture of iPS-HSCs with iPS-HPCs significantly improved hepatocytic maturation in iPS-HPCs, such as their capacity for albumin production. Next, we generated iPS cell lines overexpressing LIM homeobox 2 (LHX2), which suppresses myofibroblastic changes in HSCs in mice. Hepatocytic maturation in iPS-HPCs was significantly increased in direct co-culture with iPS-HSCs overexpressing LHX2, but not in co-culture with a human hepatic stellate cell line (LX-2) overexpressing LHX2. LHX2 regulated the expression of extracellular matrices, such as laminin and collagen, in iPS-HSCs. In conclusion, this study provides an evidence that LHX2 upregulation in iPS-HSCs promotes hepatocytic maturation of iPS-HPCs, and indicates that genetically modified iPS-HSCs will be of value for research into cell-cell interactions.

LIM Homeobox Domain 2 Is Required for Corneal Epithelial Homeostasis

The cornea requires constant epithelial renewal to maintain clarity for appropriate vision. A subset of stem cells residing at the limbus is primarily responsible for maintaining corneal epithelium homeostasis. Trauma and disease may lead to stem cell deficiency and therapeutic targeting to replenish the stemness capacity has been stalled by the lack of reliable corneal epithelial stem cell markers. Here we identified the location of Lhx2 in mice (mLhx2) cornea and conjunctival tissue using an Lhx2eGFP reporter model and in human tissues (hLHX2). Lhx2 localized to the basal cells of central cornea, the conjunctiva and the entire limbal epithelium in humans and mice. To ascribe a functional role we generated Lhx2 conditional knockout (cKO) mice and the phenotypic effects in corneas were analyzed by slit lamp microscopy, in cell‐based assays and in a model of corneal epithelium debridement. Immunodetection on corneal sections were used to visualize conjunctivalization, a sign of limbal barrier failure. Lhx2cKO mice produced reduced body hair and spontaneous epithelial defects in the cornea that included neovascularization, perforation with formation of scar tissue and opacification. Cell based assays showed that Lhx2cKO derived corneal epithelial cells have a significantly lower capacity to form colonies over time and delayed wound‐healing recovery when compared to wildtype cells. Repeated corneal epithelial wounding resulted in decreased re‐epithelialization and multiple cornea lesions in Lhx2cKO mice compared to normal recovery seen in wildtype mice. We conclude that Lhx2 is required for maintenance of the corneal epithelial cell compartment and the limbal barrier. Stem Cells2016;34:493–503

Modeling murine yolk sac hematopoiesis with embryonic stem cell culture systems

The onset of hematopoiesis in mammals is defined by generation of primitive erythrocytes and macrophage progenitors in embryonic yolk sac. Laboratories have met the challenge of transient and swiftly changing specification events from ventral mesoderm through multipotent progenitors and maturing lineage-restricted hematopoietic subtypes, by developing powerful in vitro experimental models to interrogate hematopoietic ontogeny. Most importantly, studies of differentiating embryonic stem cell derivatives in embryoid body and stromal coculture systems have identified crucial roles for transcription factor networks (e.g. Gata1, Runx1, Scl) and signaling pathways (e.g. BMP, VEGF, WNT) in controlling stem and progenitor cell output. These and other relevant pathways have pleiotropic biological effects, and are often associated with early embryonic lethality in knockout mice. Further refinement in subsequent studies has allowed conditional expression of key regulatory genes, and isolation of progenitors via cell surface markers (e.g. FLK1) and reporter-tagged constructs, with the purpose of measuring their primitive and definitive hematopoietic potential. These observations continue to inform attempts to direct the differentiation, and augment the expansion, of progenitors in human cell culture systems that may prove useful in cell replacement therapies for hematopoietic deficiencies. The purpose of this review is to survey the extant literature on the use of differentiating murine embryonic stem cells in culture to model the developmental process of yolk sac hematopoiesis.

Cyclic expression of Lhx2 is involved in secondary hair follicle development in cashmere goat

Lhx2, a member of LIM homeobox transcription factors, plays a key role in normal tissue development. However, the molecular mechanism of Lhx2 gene in the regulation of the secondary hair follicle cycling in cashmere goat remains largely unknown. In the present study, the Lhx2 gene was cloned and characterized in cashmere goat. The cloned cDNA of Lhx2 was 1233 bp in length, encoding for proteins of 406 amino acids which contained all functionally important domains conserved among vertebrate Lhx2 gene. Tissue distribution analysis showed that Lhx2 mRNA was highly expressed in the skin and low expressed in all other tissues. Immunohistochemical localization revealed that Lhx2 was expressed in secondary hair follicles. Analysis of expression profiles of Lhx2 mRNA during different development stages in secondary hair follicles showed that the highest expression was observed at the anagen stage, while the lowest expression was detected at the telogen stage. The expression tendency during the development stages was that it increased from telogen to anagen, decreased from anagen to catagen, and decreased from catagen to telogen. The expression pattern of Lhx2 protein and mRNA was similar. The mRNA and protein expression of Lhx2 were consistent throughout the development cycle in secondary hair follicles. These findings provided a better understanding of the function of Lhx2 and suggested that the cyclic expression of Lhx2 might play important roles during secondary hair follicle development in cashmere goat.

Isolation and phenotypic characterization of colorectal cancer stem cells with organ-specific metastatic potential

BACKGROUND & AIMS

Migrating cancer stem cells (MCSCs) are believed to form metastases. We sought to identify markers of MCSCs from human colorectal cancers (CRCs) and determine their roles in organ-specific metastasis.

METHODS

To identify colorectal MCSCs that contribute to organ-specific metastasis, we developed a model of liver or lung metastasis using primary tumor cells from patients with CRC who had liver and lung metastases. Distinct organ-specific metastatic cells were isolated by 6 cycles of selecting for cells that formed liver and lung tumors after subcutaneous injection into mice. Microarray analysis was used to identify markers of the organ-specific MCSCs. We then measured levels of these markers in CRC cell lines and 128 CRC samples. We characterized the functional roles of these markers in organ-specific metastasis.

RESULTS

We identified CD110 and CDCP1 as cell surface markers of MCSCs from human colorectal tumors that metastasized to liver and lung. We observed a distinct pattern of CD110 and CDCP1 in a panel of primary colorectal tumor samples and their matched liver or pulmonary metastases, indicating that these proteins might serve as biomarkers of organ-specific metastasis. Functional studies showed that thrombopoietin attracts CD110(+) CSCs and increases their self-renewal to promote formation of liver metastases. CDCP1 promoted adhesion of CRC cells to the lung endothelium.

CONCLUSIONS

We isolated MCSCs from primary human CRCs and found that the CD110(+) and CDCP1(+) subpopulations mediate organ-specific metastasis. These findings might be used to aid in selection of patients for postoperative adjuvant therapy.

Genome-wide association of body fat distribution in African ancestry populations suggests new loci

Central obesity, measured by waist circumference (WC) or waist-hip ratio (WHR), is a marker of body fat distribution. Although obesity disproportionately affects minority populations, few studies have conducted genome-wide association study (GWAS) of fat distribution among those of predominantly African ancestry (AA). We performed GWAS of WC and WHR, adjusted and unadjusted for BMI, in up to 33,591 and 27,350 AA individuals, respectively. We identified loci associated with fat distribution in AA individuals using meta-analyses of GWA results for WC and WHR (stage 1). Overall, 25 SNPs with single genomic control (GC)-corrected p-values<5.0 × 10(-6) were followed-up (stage 2) in AA with WC and with WHR. Additionally, we interrogated genomic regions of previously identified European ancestry (EA) WHR loci among AA. In joint analysis of association results including both Stage 1 and 2 cohorts, 2 SNPs demonstrated association, rs2075064 at LHX2, p = 2.24×10(-8) for WC-adjusted-for-BMI, and rs6931262 at RREB1, p = 2.48×10(-8) for WHR-adjusted-for-BMI. However, neither signal was genome-wide significant after double GC-correction (LHX2: p = 6.5 × 10(-8); RREB1: p = 5.7 × 10(-8)). Six of fourteen previously reported loci for waist in EA populations were significant (p<0.05 divided by the number of independent SNPs within the region) in AA studied here (TBX15-WARS2, GRB14, ADAMTS9, LY86, RSPO3, ITPR2-SSPN). Further, we observed associations with metabolic traits: rs13389219 at GRB14 associated with HDL-cholesterol, triglycerides, and fasting insulin, and rs13060013 at ADAMTS9 with HDL-cholesterol and fasting insulin. Finally, we observed nominal evidence for sexual dimorphism, with stronger results in AA women at the GRB14 locus (p for interaction = 0.02). In conclusion, we identified two suggestive loci associated with fat distribution in AA populations in addition to confirming 6 loci previously identified in populations of EA. These findings reinforce the concept that there are fat distribution loci that are independent of generalized adiposity.

Lhx2 balances progenitor maintenance with neurogenic output and promotes competence state progression in the developing retina

The LIM-Homeodomain transcription factor Lhx2 is an essential organizer of early eye development and is subsequently expressed in retinal progenitor cells (RPCs). To determine its requirement in RPCs, we performed a temporal series of conditional inactivations in mice with the early RPC driver Pax6 α-Cre and the tamoxifen-inducible Hes1(CreERT2) driver. Deletion of Lhx2 caused a significant reduction of the progenitor population and a corresponding increase in neurogenesis. Precursor fate choice correlated with the time of inactivation; early and late inactivation led to the overproduction of retinal ganglion cells (RGCs) and rod photoreceptors, respectively. In each case, however, the overproduction was selective, occurring at the expense of other cell types and indicating a role for Lhx2 in generating cell type diversity. RPCs that persisted in the absence of Lhx2 continued to generate RGC precursors beyond their normal production window, suggesting that Lhx2 facilitates a transition in competence state. These results identify Lhx2 as a key regulator of RPC properties that contribute to the ordered production of multiple cell types during retinal tissue formation.

Multifunctional roles of urokinase plasminogen activator (uPA) in cancer stemness and chemoresistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is almost always lethal. One of the underlying reasons for this lethality is believed to be the presence of cancer stem cells (CSC), which impart chemoresistance and promote recurrence, but the mechanisms responsible are unclear. Recently the poor prognosis of PDAC has been correlated with increased expression of urokinase plasminogen activator (uPA). In the present study we examine the role of uPA in the generation of PDAC CSC. We observe a subset of cells identifiable as a side population (SP) when sorted by flow cytometry of MIA PaCa-2 and PANC-1 pancreatic cancer cells that possess the properties of CSC. A large fraction of these SP cells are CD44 and CD24 positive, are gemcitabine resistant, possess sphere-forming ability, and exhibit increased tumorigenicity, known characteristics of cancer stemness. Increased tumorigenicity and gemcitabine resistance decrease after suppression of uPA. We observe that uPA interacts directly with transcription factors LIM homeobox-2 (Lhx2), homeobox transcription factor A5 (HOXA5), and Hey to possibly promote cancer stemness. uPA regulates Lhx2 expression by suppressing expression of miR-124 and p53 expression by repressing its promoter by inactivating HOXA5. These results demonstrate that regulation of gene transcription by uPA contributes to cancer stemness and clinical lethality.

Effect of low dose bisphenol A on the early differentiation of human embryonic stem cells into mammary epithelial cells

It has been previously reported that bisphenol A (BPA) can disturb the development of mammary structure and increase the risk of breast cancer in experimental animals. In this study, an in vitro model of human embryonic stem cell (hESC) differentiation into mammary epithelial cells was applied to investigate the effect of low dose BPA on the early stages of mammogenesis. A newly established hESC line was directionally differentiated into mammary epithelial cells by a well-established three-dimensional (3D) culture system. The differentiated mammary epithelial cells were characterized by immunofluorescence and western blotting assay, and were called induced differentiated mammary epithelial cells (iDMECs) based on these data. The hESCs were treated with low doses of BPA range 10(-9)-10(-6)M during the differentiation process, with DMSO as the solvent control and 17-β-estrodiol (E2) as the estrogen-positive control. Our results showed that low dose BPA and E2 could influence the mammosphere area of iDMECs and upregulate the expression level of Oct4 and Nanog proteins, while only BPA could downregulate the expression of E-cadherin protein. Taken together, this study provides some insights into the effects of low dose BPA on the early differentiation stage of mammary epithelial cells and suggests an easier canceration status of iDMECs under the effect of low dose BPA during its early differentiation stage.

Ascl1 (Mash1) knockout perturbs differentiation of nonneuronal cells in olfactory epithelium

The embryonic olfactory epithelium (OE) generates only a very few olfactory sensory neurons when the basic helix-loop-helix transcription factor, ASCL1 (previously known as MASH1) is eliminated by gene mutation. We have closely examined the structure and composition of the OE of knockout mice and found that the absence of neurons dramatically affects the differentiation of multiple other epithelial cell types as well. The most prominent effect is observed within the two known populations of stem and progenitor cells of the epithelium. The emergence of horizontal basal cells, a multipotent progenitor population in the adult epithelium, is anomalous in the Ascl1 knockout mice. The differentiation of globose basal cells, another multipotent progenitor population in the adult OE, is also aberrant. All of the persisting globose basal cells are marked by SOX2 expression, suggesting a prominent role for SOX2 in progenitors upstream of Ascl1. However, NOTCH1-expressing basal cells are absent from the knockout; since NOTCH1 signaling normally acts to suppress Ascl1 via HES1 and drives sustentacular (Sus) cell differentiation during adult epithelial regeneration, its absence suggests reciprocity between neurogenesis and the differentiation of Sus cells. Indeed, the Sus cells of the mutant mice express a markedly lower level of HES1, strengthening that notion of reciprocity. Duct/gland development appears normal. Finally, the expression of cKIT by basal cells is also undetectable, except in those small patches where neurogenesis escapes the effects of Ascl1 knockout and neurons are born. Thus, persistent neurogenic failure distorts the differentiation of multiple other cell types in the olfactory epithelium.

Pharyngeal mesoderm regulatory network controls cardiac and head muscle morphogenesis

The search for developmental mechanisms driving vertebrate organogenesis has paved the way toward a deeper understanding of birth defects. During embryogenesis, parts of the heart and craniofacial muscles arise from pharyngeal mesoderm (PM) progenitors. Here, we reveal a hierarchical regulatory network of a set of transcription factors expressed in the PM that initiates heart and craniofacial organogenesis. Genetic perturbation of this network in mice resulted in heart and craniofacial muscle defects, revealing robust cross-regulation between its members. We identified Lhx2 as a previously undescribed player during cardiac and pharyngeal muscle development. Lhx2 and Tcf21 genetically interact with Tbx1, the major determinant in the etiology of DiGeorge/velo-cardio-facial/22q11.2 deletion syndrome. Furthermore, knockout of these genes in the mouse recapitulates specific cardiac features of this syndrome. We suggest that PM-derived cardiogenesis and myogenesis are network properties rather than properties specific to individual PM members. These findings shed new light on the developmental underpinnings of congenital defects.

Lhx2 differentially regulates Sox9, Tcf4 and Lgr5 in hair follicle stem cells to promote epidermal regeneration after injury

The Lhx2 transcription factor plays essential roles in morphogenesis and patterning of ectodermal derivatives as well as in controlling stem cell activity. Here, we show that during murine skin morphogenesis, Lhx2 is expressed in the hair follicle (HF) buds, whereas in postnatal telogen HFs Lhx2(+) cells reside in the stem cell-enriched epithelial compartments (bulge, secondary hair germ) and co-express selected stem cell markers (Sox9, Tcf4 and Lgr5). Remarkably, Lhx2(+) cells represent the vast majority of cells in the bulge and secondary hair germ that proliferate in response to skin injury. This is functionally important, as wound re-epithelization is significantly retarded in heterozygous Lhx2 knockout (+/-) mice, whereas anagen onset in the HFs located closely to the wound is accelerated compared with wild-type mice. Cell proliferation in the bulge and the number of Sox9(+) and Tcf4(+) cells in the HFs closely adjacent to the wound in Lhx2(+/-) mice are decreased in comparison with wild-type controls, whereas expression of Lgr5 and cell proliferation in the secondary hair germ are increased. Furthermore, acceleration of wound-induced anagen development in Lhx2(+/-) mice is inhibited by administration of Lgr5 siRNA. Finally, Chip-on-chip/ChIP-qPCR and reporter assay analyses identified Sox9, Tcf4 and Lgr5 as direct Lhx2 targets in keratinocytes. These data strongly suggest that Lhx2 positively regulates Sox9 and Tcf4 in the bulge cells, and promotes wound re-epithelization, whereas it simultaneously negatively regulates Lgr5 in the secondary hair germ and inhibits HF cycling. Thus, Lhx2 operates as an important regulator of epithelial stem cell activity in the skin response to injury.

Modularity of CHIP/LDB transcription complexes regulates cell differentiation

Transcription is the first step through which the cell operates, via its repertoire of transcription complexes, to direct cellular functions and cellular identity by generating the cell-specific transcriptome. The modularity of the composition of constituents of these complexes allows the cell to delicately regulate its transcriptome. In a recent study we have examined the effects of reducing the levels of specific transcription co-factors on the function of two competing transcription complexes, namely CHIP-AP and CHIP-PNR which regulate development of cells in the thorax of Drosophila. We found that changing the availability of these co-factors can shift the balance between these complexes leading to transition from utilization of CHIP-AP to CHIP-PNR. This is reflected in change in the expression profile of target genes, altering developmental cell fates. We propose that such a mechanism may operate in normal fly development. Transcription complexes analogous to CHIP-AP and CHIP-PNR exist in mammals and we discuss how such a shift in the balance between them may operate in normal mammalian development.

In vitro generation of HSC-like cells from murine ESCs/iPSCs by enforced expression of LIM-homeobox transcription factor Lhx2

Identification of genes involved in in vitro differentiation induction of embryonic stem cells (ESCs) into hematopoietic stem cells (HSCs) has been challenged during last decade. To date, a homeobox transcription factor Hoxb4 has been only demonstrated to possess such an effect in mice. Here, we show that HSC-like cells were efficiently induced from mouse ESCs by enforced expression of Lhx2, a LIM-homeobox transcription factor. Transduction of Lhx2 into ESC-derived mesodermal cells resulted in robust differentiation of c-Kit(+)/Sca-1(+)/Lineage(-) (KSL) cells in vitro. The KSL cell induction frequency was superior to the case of Hoxb4. Furthermore, transplantation of Lhx2-transduced hematopoietic cells into lethally irradiated mice resulted in multilineage repopulation of hematopoietic cells over 4 months. Transduction of Lhx2 into induced pluripotent stem cells (iPSCs) was also effective in generating KSL cells in vitro, as well as HSC-like activities in vivo. These results demonstrate that ectopic expression of Lhx2 confers an in vivo engrafting capacity to ESC/iPSC-derived hematopoietic cells and in vivo behavior of iPSC-derived hematopoietic cells is almost identical to that of ESC-derived cells.

Enhanced generation of myeloid lineages in hematopoietic differentiation from embryonic stem cells by silencing transcriptional repressor Twist-2

The self-renewal and multilineage differentiation of embryonic stem cells (ESC) is largely governed by transcription factors or repressors. Extensive efforts have focused on elucidating critical factors that control the differentiation of specific cell lineages, for instance, myeloid lineages in hematopoietic development. In this study, we found that Twist-2, a basic helix-loop-helix (bHLH) transcription factor, plays a critical role in inhibiting the differentiation of ESC. Murine ES cells, in which Twist-2 expression is silenced by lentivirally delivered shRNA, exhibit an enhanced formation of primary embryoid bodies (EB) and enhanced differentiation into mesodermally derived hematopoietic colonies. Furthermore, Twist-2 silenced (LV-siTwist-2) ESC display significantly increased generation of myeloid lineages (Gr-1(+) and F4/80(+) cells) during in vitro hematopoietic differentiation. Treatment with the Toll-like receptor (TLR) 4 ligand synergistically stimulates the generation of primary EB formation as well as of hematopoietic progenitors differentiated from LV-siTwist-2 ES cells. Thus, this study reveals the critical role of the transcriptional repressor Twist-2 in regulating the development of myeloid lineage in hematopoietic differentiation from ESC. This study also suggests a potential strategy for directional differentiation of ESC by inhibiting a transcriptional repressor.

Cyclic expression of lhx2 regulates hair formation

Hair is important for thermoregulation, physical protection, sensory activity, seasonal camouflage, and social interactions. Hair is generated in hair follicles (HFs) and, following morphogenesis, HFs undergo cyclic phases of active growth (anagen), regression (catagen), and inactivity (telogen) throughout life. The transcriptional regulation of this process is not well understood. We show that the transcription factor Lhx2 is expressed in cells of the outer root sheath and a subpopulation of matrix cells during both morphogenesis and anagen. As the HFs enter telogen, expression becomes undetectable and reappears prior to initiation of anagen in the secondary hair germ. In contrast to previously published results, we find that Lhx2 is primarily expressed by precursor cells outside of the bulge region where the HF stem cells are located. This developmental, stage- and cell-specific expression suggests that Lhx2 regulates the generation and regeneration of hair. In support of this hypothesis, we show that Lhx2 is required for anagen progression and HF morphogenesis. Moreover, transgenic expression of Lhx2 in postnatal HFs is sufficient to induce anagen. Thus, our results reveal an alternative interpretation of Lhx2 function in HFs compared to previously published results, since Lhx2 is periodically expressed, primarily in precursor cells distinct from those in the bulge region, and is an essential positive regulator of hair formation.

Hair is generated in hair follicles, complex mini-organs in the skin that are devoted to this task. All hair follicles are generated during embryonic development. The hair follicles generate a new hair shaft by cycling through stages of regression, rest, and growth continuously throughout life. The length of the growth phase determines the length of the hair. The reason(s) for this complicated regulation of hair growth is not clear, but it has been suggested that it may accommodate seasonal variations in hair growth. In this study we have identified the transcription factor Lhx2 as an important regulator of hair formation. The Lhx2 gene is active during the growth phase of the hair follicle and is turned off during the resting phase. We confirm that Lhx2 is functionally involved in hair formation, since hair follicles where Lhx2 has been inactivated are unable to make hair. Moreover, activation of the Lhx2 gene in hair follicles induced the growth phase and hence hair formation. Thus, Lhx2 is an important regulator of hair growth.

Gene expression profiling supports the hypothesis that human ovarian surface epithelia are multipotent and capable of serving as ovarian cancer initiating cells

BACKGROUND

Accumulating evidence suggests that somatic stem cells undergo mutagenic transformation into cancer initiating cells. The serous subtype of ovarian adenocarcinoma in humans has been hypothesized to arise from at least two possible classes of progenitor cells: the ovarian surface epithelia (OSE) and/or an as yet undefined class of progenitor cells residing in the distal end of the fallopian tube.

METHODS

Comparative gene expression profiling analyses were carried out on OSE removed from the surface of normal human ovaries and ovarian cancer epithelial cells (CEPI) isolated by laser capture micro-dissection (LCM) from human serous papillary ovarian adenocarcinomas. The results of the gene expression analyses were randomly confirmed in paraffin embedded tissues from ovarian adenocarcinoma of serous subtype and non-neoplastic ovarian tissues using immunohistochemistry. Differentially expressed genes were analyzed using gene ontology, molecular pathway, and gene set enrichment analysis algorithms.

RESULTS

Consistent with multipotent capacity, genes in pathways previously associated with adult stem cell maintenance are highly expressed in ovarian surface epithelia and are not expressed or expressed at very low levels in serous ovarian adenocarcinoma. Among the over 2000 genes that are significantly differentially expressed, a number of pathways and novel pathway interactions are identified that may contribute to ovarian adenocarcinoma development.

CONCLUSIONS

Our results are consistent with the hypothesis that human ovarian surface epithelia are multipotent and capable of serving as the origin of ovarian adenocarcinoma. While our findings do not rule out the possibility that ovarian cancers may also arise from other sources, they are inconsistent with claims that ovarian surface epithelia cannot serve as the origin of ovarian cancer initiating cells.