HELLS and PRDM9 form a pioneer complex to open chromatin at meiotic recombination hot spots.

Chromatin barriers prevent spurious interactions between regulatory elements and DNA-binding proteins. One such barrier, whose mechanism for overcoming is poorly understood, is access to recombination hot spots during meiosis. Here we show that the chromatin remodeler HELLS and DNA-binding protein PRDM9 function together to open chromatin at hot spots and provide access for the DNA double-strand break (DSB) machinery. Recombination hot spots are decorated by a unique combination of histone modifications not found at other regulatory elements. HELLS is recruited to hot spots by PRDM9 and is necessary for both histone modifications and DNA accessibility at hot spots. In male mice lacking HELLS, DSBs are retargeted to other sites of open chromatin, leading to germ cell death and sterility. Together, these data provide a model for hot spot activation in which HELLS and PRDM9 form a pioneer complex to create a unique epigenomic environment of open chromatin, permitting correct placement and repair of DSBs.

Genetic control of the pluripotency epigenome determines differentiation bias in mouse embryonic stem cells.

Genetically diverse pluripotent stem cells display varied, heritable responses to differentiation cues. Here, we harnessed these disparities through derivation of mouse embryonic stem cells from the BXD genetic reference panel, along with C57BL/6J (B6) and DBA/2J (D2) parental strains, to identify loci regulating cell state transitions. Upon transition to formative pluripotency, B6 stem cells quickly dissolved naïve networks adopting gene expression modules indicative of neuroectoderm lineages, whereas D2 retained aspects of naïve pluripotency. Spontaneous formation of embryoid bodies identified divergent differentiation where B6 showed a propensity toward neuroectoderm and D2 toward definitive endoderm. Genetic mapping identified major trans-acting loci co-regulating chromatin accessibility and gene expression in both naïve and formative pluripotency. These loci distally modulated occupancy of pluripotency factors at hundreds of regulatory elements. One trans-acting locus on Chr 12 primarily impacted chromatin accessibility in embryonic stem cells, while in epiblast-like cells, the same locus subsequently influenced expression of genes enriched for neurogenesis, suggesting early chromatin priming. These results demonstrate genetically determined biases in lineage commitment and identify major regulators of the pluripotency epigenome.

Variation in histone configurations correlates with gene expression across nine inbred strains of mice.

The Diversity Outbred (DO) mice and their inbred founders are widely used models of human disease. However, although the genetic diversity of these mice has been well documented, their epigenetic diversity has not. Epigenetic modifications, such as histone modifications and DNA methylation, are important regulators of gene expression and, as such, are a critical mechanistic link between genotype and phenotype. Therefore, creating a map of epigenetic modifications in the DO mice and their founders is an important step toward understanding mechanisms of gene regulation and the link to disease in this widely used resource. To this end, we performed a strain survey of epigenetic modifications in hepatocytes of the DO founders. We surveyed four histone modifications (H3K4me1, H3K4me3, H3K27me3, and H3K27ac), as well as DNA methylation. We used ChromHMM to identify 14 chromatin states, each of which represents a distinct combination of the four histone modifications. We found that the epigenetic landscape is highly variable across the DO founders and is associated with variation in gene expression across strains. We found that epigenetic state imputed into a population of DO mice recapitulated the association with gene expression seen in the founders, suggesting that both histone modifications and DNA methylation are highly heritable mechanisms of gene expression regulation. We illustrate how DO gene expression can be aligned with inbred epigenetic states to identify putative cis-regulatory regions. Finally, we provide a data resource that documents strain-specific variation in the chromatin state and DNA methylation in hepatocytes across nine widely used strains of laboratory mice.

A role for casein kinase 2 in the mechanism underlying circadian temperature compensation.

Temperature compensation of circadian clocks is an unsolved problem with relevance to the general phenomenon of biological compensation. We identify casein kinase 2 (CK2) as a key regulator of temperature compensation of the Neurospora clock by determining that two long-standing clock mutants, chrono and period-3, displaying distinctive alterations in compensation encode the beta1 and alpha subunits of CK2, respectively. Reducing the dose of these subunits, particularly beta1, significantly alters temperature compensation without altering the enzyme's Q(10). By contrast, other kinases and phosphatases implicated in clock function do not play appreciable roles in temperature compensation. CK2 exerts its effects on the clock by directly phosphorylating FREQUENCY (FRQ), and this phosphorylation is compromised in CK2 hypomorphs. Finally, mutation of certain putative CK2 phosphosites on FRQ, shown to be phosphorylated in vivo, predictably alters temperature compensation profiles effectively phenocopying CK2 mutants.

Constitutive expression of interleukin-27 diminishes proinflammatory cytokine production without impairing effector function of engineered T cells.

Immunomodulatory cytokines can alter the tumor microenvironment and promote tumor eradication. Interleukin (IL)-27 is a pleiotropic cytokine that has potential to augment anti-tumor immunity while also facilitating anti-myeloma activity. We engineered human T cells to express a recombinant single-chain (sc)IL-27 and a synthetic antigen receptor targeting the myeloma antigen, B-cell maturation antigen, and evaluated the anti-tumor function of T cells bearing scIL-27 in vitro and in vivo. We discovered that T cells bearing scIL-27 sustained anti-tumor immunity and cytotoxicity yet manifested a profound reduction in pro-inflammatory cytokines granulocyte-macrophage colony-stimulating factor and tumor necrosis factor alpha. IL-27-expressing T cells therefore present a potential avenue to avert treatment-related toxicities commonly associated with engineered T-cell therapy due to the reduced pro-inflammatory cytokine profile.

T-cell engineered with a fully humanized B-cell maturation antigen-specific T-cell antigen coupler receptor effectively target multiple myeloma.

B-cell maturation antigen (BCMA) is a clinically validated target for multiple myeloma. T-cell engineered with chimeric antigen receptors (CARs) directed against BCMA have demonstrated robust therapeutic activity in clinical trials, but toxicities remain a significant concern for a subset of patients, supporting continued investigation of other engineered T-cell platforms that may offer equal efficacy with an improved toxicity profile. The authors recently described a BCMA-specific, T-cell-centric synthetic antigen receptor, the T-cell antigen coupler (TAC) receptor, that can be used to engineer T-cell with robust anti-myeloma activity. Here the authors describe the creation of a fully humanized BCMA-specific TAC receptor. Single-chain variable fragments (scFvs) were developed from BCMA-specific F(ab)s that were identified in a fully human phage display library. Twenty-four configurations of the F(ab)s were evaluated in a medium-throughput screening using primary T-cell, and a single F(ab), TRAC 3625, emerged as the most robust following in vitro and in vivo evaluation. An optimized BCMA-specific TAC receptor was developed through iterations of the BCMA-TAC design that evaluated a next-generation TAC scaffold sequence, different domains connecting the TAC to the 3625 scFv and different orientations of the TRAC 3625 heavy and light variable regions.

Histone methyltransferase PRDM9 is not essential for meiosis in male mice.

A hallmark of meiosis is the rearrangement of parental alleles to ensure genetic diversity in the gametes. These chromosome rearrangements are mediated by the repair of programmed DNA double-strand breaks (DSBs) as genetic crossovers between parental homologs. In mice, humans, and many other mammals, meiotic DSBs occur primarily at hotspots, determined by sequence-specific binding of the PRDM9 protein. Without PRDM9, meiotic DSBs occur near gene promoters and other functional sites. Studies in a limited number of mouse strains showed that functional PRDM9 is required to complete meiosis, but despite its apparent importance, Prdm9 has been repeatedly lost across many animal lineages. Both the reason for mouse sterility in the absence of PRDM9 and the mechanism by which Prdm9 can be lost remain unclear. Here, we explore whether mice can tolerate the loss of Prdm9 By generating Prdm9 functional knockouts in an array of genetic backgrounds, we observe a wide range of fertility phenotypes and ultimately demonstrate that PRDM9 is not required for completion of male meiosis. Although DSBs still form at a common subset of functional sites in all mice lacking PRDM9, meiotic outcomes differ substantially. We speculate that DSBs at functional sites are difficult to repair as a crossover and that by increasing the efficiency of crossover formation at these sites, genetic modifiers of recombination rates can allow for meiotic progression. This model implies that species with a sufficiently high recombination rate may lose Prdm9 yet remain fertile.

Development of a B-cell maturation antigen-specific T-cell antigen coupler receptor for multiple myeloma.

BACKGROUND AIMS: T cells engineered with synthetic receptors have delivered powerful therapeutic results for patients with relapsed/refractory hematologic malignancies. The authors have recently described the T-cell antigen coupler (TAC) receptor, which co-opts the endogenous T-cell receptor (TCR) and activates engineered T cells in an HLA-independent manner. Here the authors describe the evolution of a next-generation TAC receptor with a focus on developing a TAC-engineered T cell for multiple myeloma. METHODS: To optimize the TAC scaffold, the authors employed a bona fide antigen-binding domain derived from the B-cell maturation antigen-specific monoclonal antibody C11D5.3, which has been used successfully in the clinic. The authors first tested humanized versions of the UCHT1 domain, which is used by the TAC to co-opt the TCR. The authors further discovered that the signal peptide affected surface expression of the TAC receptor. Higher density of the TAC receptor enhanced target binding in vitro, which translated into higher levels of Lck at the immunological synapse and stronger proliferation when only receptor-ligand interactions were present. RESULTS: The authors observed that the humanized UCHT1 improved surface expression and in vivo efficacy. Using TAC T cells derived from both healthy donors and multiple myeloma patients, the authors determined that despite the influence of receptor density on early activation events and effector function, receptor density did not impact late effector functions in vitro, nor did the receptor density affect in vivo efficacy. CONCLUSIONS: The modifications to the TAC scaffold described herein represent an important step in the evolution of this technology, which tolerates a range of expression levels without impacting therapeutic efficacy.

The Meiotic Recombination Activator PRDM9 Trimethylates Both H3K36 and H3K4 at Recombination Hotspots In Vivo.

In many mammals, including humans and mice, the zinc finger histone methyltransferase PRDM9 performs the first step in meiotic recombination by specifying the locations of hotspots, the sites of genetic recombination. PRDM9 binds to DNA at hotspots through its zinc finger domain and activates recombination by trimethylating histone H3K4 on adjacent nucleosomes through its PR/SET domain. Recently, the isolated PR/SET domain of PRDM9 was shown capable of also trimethylating H3K36 in vitro, raising the question of whether this reaction occurs in vivo during meiosis, and if so, what its function might be. Here, we show that full-length PRDM9 does trimethylate H3K36 in vivo in mouse spermatocytes. Levels of H3K4me3 and H3K36me3 are highly correlated at hotspots, but mutually exclusive elsewhere. In vitro, we find that although PRDM9 trimethylates H3K36 much more slowly than it does H3K4, PRDM9 is capable of placing both marks on the same histone molecules. In accord with these results, we also show that PRDM9 can trimethylate both K4 and K36 on the same nucleosomes in vivo, but the ratio of K4me3/K36me3 is much higher for the pair of nucleosomes adjacent to the PRDM9 binding site compared to the next pair further away. Importantly, H3K4me3/H3K36me3-double-positive nucleosomes occur only in regions of recombination: hotspots and the pseudoautosomal (PAR) region of the sex chromosomes. These double-positive nucleosomes are dramatically reduced when PRDM9 is absent, showing that this signature is PRDM9-dependent at hotspots; the residual double-positive nucleosomes most likely come from the PRDM9-independent PAR. These results, together with the fact that PRDM9 is the only known mammalian histone methyltransferase with both H3K4 and H3K36 trimethylation activity, suggest that trimethylation of H3K36 plays an important role in the recombination process. Given the known requirement of H3K36me3 for double strand break repair by homologous recombination in somatic cells, we suggest that it may play the same role in meiosis.

Multimer Formation Explains Allelic Suppression of PRDM9 Recombination Hotspots.

Genetic recombination during meiosis functions to increase genetic diversity, promotes elimination of deleterious alleles, and helps assure proper segregation of chromatids. Mammalian recombination events are concentrated at specialized sites, termed hotspots, whose locations are determined by PRDM9, a zinc finger DNA-binding histone methyltransferase. Prdm9 is highly polymorphic with most alleles activating their own set of hotspots. In populations exhibiting high frequencies of heterozygosity, questions remain about the influences different alleles have in heterozygous individuals where the two variant forms of PRDM9 typically do not activate equivalent populations of hotspots. We now find that, in addition to activating its own hotspots, the presence of one Prdm9 allele can modify the activity of hotspots activated by the other allele. PRDM9 function is also dosage sensitive; Prdm9+/- heterozygous null mice have reduced numbers and less active hotspots and increased numbers of aberrant germ cells. In mice carrying two Prdm9 alleles, there is allelic competition; the stronger Prdm9 allele can partially or entirely suppress chromatin modification and recombination at hotspots of the weaker allele. In cell cultures, PRDM9 protein variants form functional heteromeric complexes which can bind hotspots sequences. When a heteromeric complex binds at a hotspot of one PRDM9 variant, the other PRDM9 variant, which would otherwise not bind, can still methylate hotspot nucleosomes. We propose that in heterozygous individuals the underlying molecular mechanism of allelic suppression results from formation of PRDM9 heteromers, where the DNA binding activity of one protein variant dominantly directs recombination initiation towards its own hotspots, effectively titrating down recombination by the other protein variant. In natural populations with many heterozygous individuals, allelic competition will influence the recombination landscape.

PRDM9 drives evolutionary erosion of hotspots in Mus musculus through haplotype-specific initiation of meiotic recombination.

Meiotic recombination generates new genetic variation and assures the proper segregation of chromosomes in gametes. PRDM9, a zinc finger protein with histone methyltransferase activity, initiates meiotic recombination by binding DNA at recombination hotspots and directing the position of DNA double-strand breaks (DSB). The DSB repair mechanism suggests that hotspots should eventually self-destruct, yet genome-wide recombination levels remain constant, a conundrum known as the hotspot paradox. To test if PRDM9 drives this evolutionary erosion, we measured activity of the Prdm9Cst allele in two Mus musculus subspecies, M.m. castaneus, in which Prdm9Cst arose, and M.m. domesticus, into which Prdm9Cst was introduced experimentally. Comparing these two strains, we find that haplotype differences at hotspots lead to qualitative and quantitative changes in PRDM9 binding and activity. Using Mus spretus as an outlier, we found most variants affecting PRDM9Cst binding arose and were fixed in M.m. castaneus, suppressing hotspot activity. Furthermore, M.m. castaneus×M.m. domesticus F1 hybrids exhibit novel hotspots, with large haplotype biases in both PRDM9 binding and chromatin modification. These novel hotspots represent sites of historic evolutionary erosion that become activated in hybrids due to crosstalk between one parent's Prdm9 allele and the opposite parent's chromosome. Together these data support a model where haplotype-specific PRDM9 binding directs biased gene conversion at hotspots, ultimately leading to hotspot erosion.

PRDM9 binding organizes hotspot nucleosomes and limits Holliday junction migration.

In mammals, genetic recombination during meiosis is limited to a set of 1- to 2-kb regions termed hotspots. Their locations are predominantly determined by the zinc finger protein PRDM9, which binds to DNA in hotspots and subsequently uses its SET domain to locally trimethylate histone H3 at lysine 4 (H3K4me3). This sets the stage for double-strand break (DSB) formation and reciprocal exchange of DNA between chromatids, forming Holliday junctions. Here we report genome-wide analyses of PRDM9-dependent histone modifications using two inbred mouse strains differing only in their PRDM9 zinc finger domain. We show that PRDM9 binding actively reorganizes nucleosomes into a symmetrical pattern, creating an extended nucleosome-depleted region. These regions are centered by a consensus PRDM9 binding motif, whose location and identity was confirmed in vitro. We also show that DSBs are centered over the PRDM9 binding motif within the nucleosome-depleted region. Combining these results with data from genetic crosses, we find that crossing-over is restricted to the region marked by H3K4me3. We suggest that PRDM9-modified nucleosomes create a permissible environment that first directs the location of DSBs and then defines the boundaries of Holliday junction branch migration.

Quantitative proteomics reveals a dynamic interactome and phase-specific phosphorylation in the Neurospora circadian clock.

Circadian systems are comprised of multiple proteins functioning together to produce feedback loops driving robust, approximately 24 hr rhythms. In all circadian systems, proteins in these loops are regulated through myriad physically and temporally distinct posttranslational modifications (PTMs). To better understand how PTMs impact a circadian oscillator, we implemented a proteomics-based approach by combining purification of endogenous FREQUENCY (FRQ) and its interacting partners with quantitative mass spectrometry (MS). We identify and quantify time-of-day-specific protein-protein interactions in the clock and show how these provide a platform for temporal and physical separation between the dual roles of FRQ. Additionally, by unambiguously identifying over 75 phosphorylated residues, following their quantitative change over a circadian cycle, and examining the phenotypes of strains that have lost these sites, we demonstrate how spatially and temporally regulated phosphorylation has opposing effects directly on overt circadian rhythms and FRQ stability.

Nuclear localization of PRDM9 and its role in meiotic chromatin modifications and homologous synapsis.

Developmental progress of germ cells through meiotic phases is closely tied to ongoing meiotic recombination. In mammals, recombination preferentially occurs in genomic regions known as hotspots; the protein that activates these hotspots is PRDM9, containing a genetically variable zinc finger (ZNF) domain and a PR-SET domain with histone H3K4 trimethyltransferase activity. PRDM9 is required for fertility in mice, but little is known about its localization and developmental dynamics. Application of spermatogenic stage-specific markers demonstrates that PRDM9 accumulates in male germ cell nuclei at pre-leptonema to early leptonema but is no longer detectable in nuclei by late zygonema. By the pachytene stage, PRDM9-dependent histone H3K4 trimethyl marks on hotspots also disappear. PRDM9 localizes to nuclei concurrently with the deposition of meiotic cohesin complexes, but is not required for incorporation of cohesin complex proteins into chromosomal axial elements, or accumulation of normal numbers of RAD51 foci on meiotic chromatin by late zygonema. Germ cells lacking PRDM9 exhibit inefficient homology recognition and synapsis, with aberrant repair of meiotic DNA double-strand breaks and transcriptional abnormalities characteristic of meiotic silencing of unsynapsed chromatin. Together, these results on the developmental time course for nuclear localization of PRDM9 establish its direct window of function and demonstrate the independence of chromosome axial element formation from the concurrent PRDM9-mediated activation of recombination hotspots.

Post-translational modifications in circadian rhythms.

The pace has quickened in circadian biology research. In particular, an abundance of results focused on post-translational modifications (PTMs) is sharpening our view of circadian molecular clockworks. PTMs affect nearly all aspects of clock biology; in some cases they are essential for clock function and in others, they provide layers of regulatory fine-tuning. Our goal is to review recent advances in clock PTMs, help make sense of emerging themes, and spotlight intriguing (and perhaps controversial) new findings. We focus on PTMs affecting the core functions of eukaryotic clocks, in particular the functionally related oscillators in Neurospora crassa, Drosophila melanogaster, and mammalian cells.

Imputation of 3D genome structure by genetic-epigenetic interaction modeling in mice.

Gene expression is known to be affected by interactions between local genetic variation and DNA accessibility, with the latter organized into three-dimensional chromatin structures. Analyses of these interactions have previously been limited, obscuring their regulatory context, and the extent to which they occur throughout the genome. Here, we undertake a genome-scale analysis of these interactions in a genetically diverse population to systematically identify global genetic-epigenetic interaction, and reveal constraints imposed by chromatin structure. We establish the extent and structure of genotype-by-epigenotype interaction using embryonic stem cells derived from Diversity Outbred mice. This mouse population segregates millions of variants from eight inbred founders, enabling precision genetic mapping with extensive genotypic and phenotypic diversity. With 176 samples profiled for genotype, gene expression, and open chromatin, we used regression modeling to infer genetic-epigenetic interactions on a genome-wide scale. Our results demonstrate that statistical interactions between genetic variants and chromatin accessibility are common throughout the genome. We found that these interactions occur within the local area of the affected gene, and that this locality corresponds to topologically associated domains (TADs). The likelihood of interaction was most strongly defined by the three-dimensional (3D) domain structure rather than linear DNA sequence. We show that stable 3D genome structure is an effective tool to guide searches for regulatory elements and, conversely, that regulatory elements in genetically diverse populations provide a means to infer 3D genome structure. We confirmed this finding with CTCF ChIP-seq that revealed strain-specific binding in the inbred founder mice. In stem cells, open chromatin participating in the most significant regression models demonstrated an enrichment for developmental genes and the TAD-forming CTCF-binding complex, providing an opportunity for statistical inference of shifting TAD boundaries operating during early development. These findings provide evidence that genetic and epigenetic factors operate within the context of 3D chromatin structure.

Enhlink infers distal and context-specific enhancer-promoter linkages.

Enhancers play a crucial role in regulating gene expression and their functional status can be queried with cell type precision using using single-cell (sc)ATAC-seq. To facilitate analysis of such data, we developed Enhlink, a novel computational approach that leverages single-cell signals to infer linkages between regulatory DNA sequences, such as enhancers and promoters. Enhlink uses an ensemble strategy that integrates cell-level technical covariates to control for batch effects and biological covariates to infer robust condition-specific links and their associated p-values. It can integrate simultaneous gene expression and chromatin accessibility measurements of individual cells profiled by multi-omic experiments for increased specificity. We evaluated Enhlink using simulated and real scATAC-seq data, including those paired with physical enhancer-promoter links enumerated by promoter capture Hi-C and with multi-omic scATAC-/RNA-seq data we generated from the mouse striatum. These examples demonstrated that our method outperforms popular alternative strategies. In conjunction with eQTL analysis, Enhlink revealed a putative super-enhancer regulating key cell type-specific markers of striatal neurons. Taken together, our analyses demonstrate that Enhlink is accurate, powerful, and provides features that can lead to novel biological insights.

Genetic dissection of the pluripotent proteome through multi-omics data integration.

Genetic background drives phenotypic variability in pluripotent stem cells (PSCs). Most studies to date have used transcript abundance as the primary molecular readout of cell state in PSCs. We performed a comprehensive proteogenomics analysis of 190 genetically diverse mouse embryonic stem cell (mESC) lines. The quantitative proteome is highly variable across lines, and we identified pluripotency-associated pathways that were differentially activated in the proteomics data that were not evident in transcriptome data from the same lines. Integration of protein abundance to transcript levels and chromatin accessibility revealed broad co-variation across molecular layers as well as shared and unique drivers of quantitative variation in pluripotency-associated pathways. Quantitative trait locus (QTL) mapping localized the drivers of these multi-omic signatures to genomic hotspots. This study reveals post-transcriptional mechanisms and genetic interactions that underlie quantitative variability in the pluripotent proteome and provides a regulatory map for mESCs that can provide a basis for future mechanistic studies.

LCL161 enhances expansion and survival of engineered anti-tumor T cells but is restricted by death signaling.

Background: The genesis of SMAC mimetic drugs is founded on the observation that many cancers amplify IAP proteins to facilitate their survival, and therefore removal of these pathways would re-sensitize the cells towards apoptosis. It has become increasingly clear that SMAC mimetics also interface with the immune system in a modulatory manner. Suppression of IAP function by SMAC mimetics activates the non-canonical NF-κB pathway which can augment T cell function, opening the possibility of using SMAC mimetics to enhance immunotherapeutics. Methods: We have investigated the SMAC mimetic LCL161, which promotes degradation of cIAP-1 and cIAP-2, as an agent for delivering transient costimulation to engineered BMCA-specific human TAC T cells. In doing so we also sought to understand the cellular and molecular effects of LCL161 on T cell biology. Results: LCL161 activated the non-canonical NF-κB pathway and enhanced antigen-driven TAC T cell proliferation and survival. Transcriptional profiling from TAC T cells treated with LCL161 revealed differential expression of costimulatory and apoptosis-related proteins, namely CD30 and FAIM3. We hypothesized that regulation of these genes by LCL161 may influence the drug's effects on T cells. We reversed the differential expression through genetic engineering and observed impaired costimulation by LCL161, particularly when CD30 was deleted. While LCL161 can provide a costimulatory signal to TAC T cells following exposure to isolated antigen, we did not observe a similar pattern when TAC T cells were stimulated with myeloma cells expressing the target antigen. We questioned whether FasL expression by myeloma cells may antagonize the costimulatory effects of LCL161. Fas-KO TAC T cells displayed superior expansion following antigen stimulation in the presence of LCL161, suggesting a role for Fas-related T cell death in limiting the magnitude of the T cell response to antigen in the presence of LCL161. Conclusions: Our results demonstrate that LCL161 provides costimulation to TAC T cells exposed to antigen alone, however LCL161 did not enhance TAC T cell anti-tumor function when challenged with myeloma cells and may be limited due to sensitization of T cells towards Fas-mediated apoptosis.

Glucagon-like peptide-2 increases intestinal lipid absorption and chylomicron production via CD36.

BACKGROUND & AIMS: Excessive postprandial lipemia is a prevalent condition that results from intestinal oversecretion of apolipoprotein B48 (apoB48)-containing lipoproteins. Glucagon-like peptide-2 (GLP-2) is a gastrointestinal-derived intestinotropic hormone that links nutrient absorption to intestinal structure and function. We investigated the effects of GLP-2 on intestinal lipid absorption and lipoprotein production. METHODS: Intestinal lipid absorption and chylomicron production were quantified in hamsters, wild-type mice, and Cd36(-/-) mice infused with exogenous GLP-2. Newly synthesized apoB48 was metabolically labelled in primary hamster jejunal fragments. Fatty acid absorption was measured, and putative fatty acid transporters were assessed by immunoblotting. RESULTS: Human GLP-2 increased secretion of the triglyceride (TG)-rich lipoprotein (TRL)-apoB48 following oral administration of olive oil to hamsters; TRL and cholesterol mass each increased 3-fold. Fast protein liquid chromatography profiling indicated that GLP-2 stimulated secretion of chylomicron/very low-density lipoprotein-sized particles. Moreover, GLP-2 directly stimulated apoB48 secretion in jejunal fragments cultured ex vivo, increased expression of fully glycosylated cluster of differentiation 36/fatty acid translocase (CD36), and induced intestinal absorption of [(3)H]triolein. The ability of GLP-2 to increase intestinal lipoprotein production was lost in Cd36(-/-) mice. CONCLUSIONS: GLP-2 stimulates intestinal apoB48-containing lipoprotein secretion, possibly through increased lipid uptake, via a pathway that requires CD36. These findings suggest that GLP-2 represents a nutrient-dependent signal that regulates intestinal lipid absorption and the assembly and secretion of TRLs from intestinal enterocytes.