The mammary gland is composed of basal cells and luminal cells. It is generally believed that the mammary gland arises from embryonic multipotent progenitors, but it remains unclear when lineage ...restriction occurs and what mechanisms are responsible for the switch from multipotency to unipotency during its morphogenesis. Here, we perform multicolour lineage tracing and assess the fate of single progenitors, and demonstrate the existence of a developmental switch from multipotency to unipotency during embryonic mammary gland development. Molecular profiling and single cell RNA-seq revealed that embryonic multipotent progenitors express a unique hybrid basal and luminal signature and the factors associated with the different lineages. Sustained p63 expression in embryonic multipotent progenitors promotes unipotent basal cell fate and was sufficient to reprogram adult luminal cells into basal cells by promoting an intermediate hybrid multipotent-like state. Altogether, this study identifies the timing and the mechanisms mediating early lineage segregation of multipotent progenitors during mammary gland development.
The mammary gland (MG) is composed of different cell lineages, including the basal and the luminal cells (LCs) that are maintained by distinct stem cell (SC) populations. LCs can be subdivided into ...estrogen receptor (ER)+ and ER− cells. LCs act as the cancer cell of origin in different types of mammary tumors. It remains unclear whether the heterogeneity found in luminal-derived mammary tumors arises from a pre-existing heterogeneity within LCs. To investigate LC heterogeneity, we used lineage tracing to assess whether the ER+ lineage is maintained by multipotent SCs or by lineage-restricted SCs. To this end, we generated doxycycline-inducible ER-rtTA mice that allowed us to perform genetic lineage tracing of ER+ LCs and study their fate and long-term maintenance. Our results show that ER+ cells are maintained by lineage-restricted SCs that exclusively contribute to the expansion of the ER+ lineage during puberty and their maintenance during adult life.
Display omitted
•ER+ stem cells mediate expansion and maintenance of the ER+ lineage•ER+ stem cells expand and differentiate into ER+ cells following transplantation•ER+ stem cells survive involution and repopulate the ER+ lineage
Van Keymeulen et al. performed lineage tracing of estrogen receptor (ER)-expressing cells in the mammary gland. They show that the ER+ cells are maintained by lineage-restricted stem cells that exclusively contribute to the expansion of the ER+ lineage during puberty and to their maintenance during adult life.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In colorectal cancer (CRC), WNT pathway activation by genetic rearrangements of RSPO3 is emerging as a promising target. However, its low prevalence severely limits availability of preclinical models ...for in‐depth characterization. Using a pipeline designed to suppress stroma‐derived signal, we find that RSPO3 “outlier” expression in CRC samples highlights translocation and fusion transcript expression. Outlier search in 151 CRC cell lines identified VACO6 and SNU1411 cells as carriers of, respectively, a canonical PTPRK(e1)‐RSPO3(e2) fusion and a novel PTPRK(e13)‐RSPO3(e2) fusion. Both lines displayed marked in vitro and in vivo sensitivity to WNT blockade by the porcupine inhibitor LGK974, associated with transcriptional and morphological evidence of WNT pathway suppression. Long‐term treatment of VACO6 cells with LGK974 led to the emergence of a resistant population carrying two frameshift deletions of the WNT pathway inhibitor AXIN1, with consequent protein loss. Suppression of AXIN1 in parental VACO6 cells by RNA interference conferred marked resistance to LGK974. These results provide the first mechanism of secondary resistance to WNT pathway inhibition.
Synopsis
In colorectal cancer (CRC), translocations of the RSPO3 gene, leading to its expression as a fusion transcript, pinpoint a therapeutically actionable mechanism of Wnt pathway activation.
RSPO3 “outlier” expression analysis allowed identification of CRC cases featuring RSPO3 rearrangements.
CRC cell lines with RSPO3 rearrangements were identified and found to be sensitive to Wnt ligand deprivation induced by PORCN inhibition.
Secondary resistance to WNT pathway blockade was associated with loss‐of‐function mutations in the AXIN1 gene.
In colorectal cancer (CRC), translocations of the RSPO3 gene, leading to its expression as a fusion transcript, pinpoint a therapeutically actionable mechanism of Wnt pathway activation.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Glandular epithelia, including the mammary and prostate glands, are composed of basal cells (BCs) and luminal cells (LCs)
. Many glandular epithelia develop from multipotent basal stem cells (BSCs) ...that are replaced in adult life by distinct pools of unipotent stem cells
. However, adult unipotent BSCs can reactivate multipotency under regenerative conditions and upon oncogene expression
. This suggests that an active mechanism restricts BSC multipotency under normal physiological conditions, although the nature of this mechanism is unknown. Here we show that the ablation of LCs reactivates the multipotency of BSCs from multiple epithelia both in vivo in mice and in vitro in organoids. Bulk and single-cell RNA sequencing revealed that, after LC ablation, BSCs activate a hybrid basal and luminal cell differentiation program before giving rise to LCs-reminiscent of the genetic program that regulates multipotency during embryonic development
. By predicting ligand-receptor pairs from single-cell data
, we find that TNF-which is secreted by LCs-restricts BC multipotency under normal physiological conditions. By contrast, the Notch, Wnt and EGFR pathways were activated in BSCs and their progeny after LC ablation; blocking these pathways, or stimulating the TNF pathway, inhibited regeneration-induced BC multipotency. Our study demonstrates that heterotypic communication between LCs and BCs is essential to maintain lineage fidelity in glandular epithelial stem cells.
Full text
Available for:
FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Sympathetic activation during cold exposure increases adipocyte thermogenesis via the expression of mitochondrial protein uncoupling protein 1 (UCP1)
. The propensity of adipocytes to express UCP1 is ...under a critical influence of the adipose microenvironment and varies between sexes and among various fat depots
. Here we report that mammary gland ductal epithelial cells in the adipose niche regulate cold-induced adipocyte UCP1 expression in female mouse subcutaneous white adipose tissue (scWAT). Single-cell RNA sequencing shows that glandular luminal epithelium subtypes express transcripts that encode secretory factors controlling adipocyte UCP1 expression under cold conditions. We term these luminal epithelium secretory factors 'mammokines'. Using 3D visualization of whole-tissue immunofluorescence, we reveal sympathetic nerve-ductal contact points. We show that mammary ducts activated by sympathetic nerves limit adipocyte UCP1 expression via the mammokine lipocalin 2. In vivo and ex vivo ablation of mammary duct epithelium enhance the cold-induced adipocyte thermogenic gene programme in scWAT. Since the mammary duct network extends throughout most of the scWAT in female mice, females show markedly less scWAT UCP1 expression, fat oxidation, energy expenditure and subcutaneous fat mass loss compared with male mice, implicating sex-specific roles of mammokines in adipose thermogenesis. These results reveal a role of sympathetic nerve-activated glandular epithelium in adipocyte UCP1 expression and suggest that mammary duct luminal epithelium has an important role in controlling glandular adiposity.
Full text
Available for:
GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
Abstract
In colorectal cancer (CRC), WNT pathway activation by genetic rearrangements of RSPO3 is emerging as a promising target. However, its low prevalence severely limits availability of ...preclinical models for in-depth characterization. Using a pipeline designed to suppress stroma-derived signal, we find that RSPO3 “outlier” expression in CRC samples highlights translocation and fusion transcript expression. Outlier search in 151 CRC cell lines identified VACO6 and SNU1411cells as carriers of, respectively, a canonical PTPRK(e1)-RSPO3(e2) fusion and a novel PTPRK(e13)-RSPO3(e2) fusion. Both lines displayed marked in vitro and in vivo sensitivity to WNT blockade by the porcupine inhibitor LGK974, associated with transcriptional and morphological evidences of WNT pathway suppression. Long-term treatment of VACO6 cells with LGK974 led to the emergence of a resistant population carrying two frameshift deletions of the WNT pathway inhibitor AXIN1, with consequent protein loss. Suppression of AXIN1 in parental VACO6 cells by RNA interference conferred marked resistance to LGK974. These results provide the first mechanism of secondary resistance to WNT pathway inhibition.
Citation Format: Gabriele Picco, Consalvo Petti, Alessia Centonze, Erica Torchiaro, Alberto Bardelli, Enzo Medico. Loss of Axin1 drives acquired resistance to WNT pathway blockade in colorectal cancer cells carrying RSPO3 fusions abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3151. doi:10.1158/1538-7445.AM2017-3151
The first catalytic enantioselective and diastereoselective synthesis of atropisomeric hydrazides was achieved using a sequential catalysis protocol. This strategy is based on a one‐pot sequence of ...two organocatalytic cycles featuring the enamine amination of branched aldehydes followed by nitrogen alkylation under phase‐transfer conditions. The resulting axially chiral hydrazides were obtained directly from commercially available reagents in high yields and with good stereocontrol. The permutation of organocatalysts allowed easy access to all stereoisomers, enabling a stereodivergent approach to enantioenriched atropisomeric hydrazides.
The first enantioselective and diastereoselective synthesis of atropisomeric hydrazides was performed using one‐pot sequential catalysis based on the enamine amination of branched aldehydes followed by phase‐transfer N‐alkylation. Chiral hydrazides were obtained with high yields and stereocontrol using commercially available reagents and catalysts. The permutation of catalysts allowed for a stereodivergent approach to a new class of atropisomers.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
N-N atropisomers represent a useful class of compounds that has recently received important attention from many research groups. This article presents an in-depth analysis of the energy barrier ...needed for the racemization process of atropoisomeric hydrazides, combining an experimental and computational approach. The focus is on examining how electronic and steric factors impact the racemization process. The results obtained indicate that the barrier observed during the racemization process mainly arises from an increase in the p-orbital character of the nitrogen atoms.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
PDF
