Long-term efficacy (up to 68 weeks) of Baricitinib in combination with topical corticosteroids in adult patients with moderate-to-severe atopic dermatitis: Analysis of treatment responders, partial responders and nonresponders originating from study BREEZE-AD7.

BACKGROUND: Baricitinib demonstrated efficacy in treating adults with moderate-to-severe atopic dermatitis (AD) in Phase 3 clinical trials. OBJECTIVE: To examine long-term efficacy of baricitinib combined with topical corticosteroids (TCS) in adult patients from a Phase 3 study, BREEZE-AD7 (NCT03733301), enrolled in ongoing extension study, BREEZE-AD3 (NCT03334435). METHODS: Upon BREEZE-AD7 completion, responders or partial responders (RPR [vIGA-AD™ ≤2]) receiving baricitinib 2-mg or 4-mg + TCS maintained their original treatment doses in BREEZE-AD3. Nonresponders (NR; vIGA-AD 3,4) receiving baricitinib 2-mg were rerandomized 1:1 to baricitinib 2-mg or 4-mg; NR receiving baricitinib 4-mg remained on same dose. Integrated data from all patients (RPR + NR = baricitinib 4-mg intent-to-treat [ITT] cohort) receiving continuous baricitinib 4-mg in BREEZE-AD7 through BREEZE-AD3 were analysed, along with baricitinib 4-mg or 2-mg RPR cohorts. Primary endpoint was proportion of patients with vIGA-AD (0,1) at Weeks 16, 36 and 52 (Weeks 32, 52 and 68 of continuous therapy). Additional outcomes included improvement in EASI75 and Itch NRS (up to Week 32). Missing data were imputed by last observation carried forward. RESULTS: In baricitinib 4-mg ITT cohort (N = 102), proportions of patients achieving vIGA-AD (0,1) at Week 32, Week 52, and Week 68 were 21.6%, 26.5% and 23.5%; EASI75 were 46.1%, 40.2% and 43.1%, respectively. Itch NRS ≥4-point improvement (Itch ≥4) were 47.3% at Week 16 and 40.6% at Week 32. In baricitinib 4-mg RPR cohort (N = 63), proportions of patients achieving vIGA-AD (0,1) at Week 32, Week 52 and Week 68 were 31.7%, 33.3% 34.9%, respectively; EASI75 were 57.1%, 49.2% and 49.2%, respectively. Itch ≥4 were 53.6% at Week 16 and 46.4% at Week 32. Corresponding proportions for baricitinib 2-mg RPR cohort (N = 53) for vIGA-AD (0,1) were 39.6%, 45.3% and 30.2%; EASI75 were 77.4%, 69.8% and 58.5%, respectively. Itch ≥4 were 56.3% at Week 16 and 47.9% at Week 32. CONCLUSION: Baricitinib 4-mg and 2-mg combined with TCS maintained clinically meaningful sustained efficacy over 68 weeks of continuous treatment.

Childbearing in radiology training and early career: Challenges, opportunities, and finding the best time for you.

For many women, radiology residency occurs during the childbearing years and they often question when is the best time to have children. Anxiety regarding fertility and pregnancy-related complications contribute to early career burnout in women physicians and many have fertility regrets. Supporting radiologists in training and early in their career as they navigate pregnancy and childbearing is critical to achieving a diverse workforce and leadership. Herein, we explore career-related challenges of childbearing and highlight opportunities for radiologists in residency, fellowship, and early in their career, so that they can make an informed childbearing decision.

Same day barium esophagography and high-resolution manometry during the COVID-19 pandemic.

PURPOSE: Double contrast barium esophagography (BAS) and high-resolution manometry (HRM) are traditionally performed on separate days to allow for pre-procedural fasting. In an effort to minimize COVID-19 exposure and improve appointment efficiency with required pre-procedure testing, we permitted same day HRM prior to BAS. Our study aimed to evaluate the adequacy of barium mucosal coating with same day HRM prior to BAS compared to BAS alone. METHODS: We performed a retrospective pilot cohort study including 14 patients undergoing same day HRM prior to BAS and 20 patients undergoing BAS alone over an 8-month interval during the COVID-19 pandemic. Three abdominal imaging subspecialty-trained radiologists blindly reviewed the images and graded adequacy of esophageal coating on a 4-point scale with a score of 1 representing inadequate coating and 4 representing optimal coating. RESULTS: For the cohort studied thus far, the mean grade of the HRM and BAS group was 3.17 with a standard deviation of 0.66. The mean grade of the BAS alone group was 3.13 with a standard deviation of 0.79. There was no statistical difference in the adequacy of esophageal coating between the two groups (p-value 0.97). CONCLUSION: Same day HRM prior to BAS has no detrimental effect on barium mucosal coating compared to BAS alone. Though created to limit patient exposures during the COVID pandemic, same day BAS and HRM may prevent delays in care and improve convenience towards improved patient-centered care beyond the pandemic.

Insights into adult atopic dermatitis heterogeneity derived from circulating biomarker profiling in patients with moderate-to-severe disease.

Atopic dermatitis (AD) is a heterogeneous systemic inflammatory skin disease associated with dysregulated immune responses, barrier dysfunction and activated sensory nerves. To characterize circulating inflammatory profiles and underlying systemic disease heterogeneity within AD patients, blood samples from adult patients (N = 123) with moderate-to-severe AD in a phase 2 study of baricitinib (JAHG) were analysed. Baseline levels of 131 markers were evaluated using high-throughput and ultrasensitive proteomic platforms, patient clusters were generated based on these peripheral markers. We implemented a novel cluster reproducibility method to validate cluster outcomes within our study and used publicly available AD biomarker data set (73 markers, N = 58 patients) to validate our findings. Cluster reproducibility analysis demonstrated best consistency for 2 clusters by k-means, reproducibility of this clustering outcome was validated in an independent patient cohort. These unique JAHG patient subgroups either possessed elevated pro-inflammatory mediators, notably TNFß, MCP-3 and IL-13, among a variety of immune responses (high inflammatory) or lower levels of inflammatory biomarkers (low inflammatory). The high inflammatory subgroup was associated with greater baseline disease severity, demonstrated by greater EASI, SCORAD Index, Itch NRS and DLQI scores, compared with low inflammatory subgroup. African-American patients were predominantly associated with the high inflammatory subgroup and increased baseline disease severity. In patients with moderate-to-severe AD, heterogeneity was identified by the detection of 2 disease subgroups, differential clustering amongst ethnic groups and elevated pro-inflammatory mediators extending beyond traditional polarized immune responses. Therapeutic strategies targeting multiple pro-inflammatory cytokines may be needed to address this heterogeneity.

Fusion of high B-value diffusion-weighted and T2-weighted MR images increases sensitivity for identification of extraprostatic disease in prostate cancer.

PURPOSE: To evaluate whether fusion of high b-value diffusion-weighted imaging (DWI) and T2-weighted imaging (T2WI) increases radiologists' ability to detect pathologic features responsible for upstaging in prostate cancer patients prior to radical prostatectomy (RP). BASIC PROCEDURES: This was a retrospective study including 103 patients who underwent RP and a prostate MRI performed at 3T. High b-value DWI and T2WI were fused and interpreted by three radiologists with different degrees of experience. Prior to and after fusion, readers answered questionnaires about cancer presence, extraprostatic extension (EPE), seminal vesicle (SV) invasion, lymph node (LN) involvement, and reader confidence. Pathology reports served as the reference standard. MAIN FINDINGS: High b-value DWI-T2WI fusion increased sensitivity for detection of EPE from 65.6% to 77.4% (p < 0.05), SV invasion from 40.5% to 48.8% (p < 0.05), and LN metastasis by 23.8% to 44.4% (p < 0.05). Readers' confidence significantly improved with the use of fusion imaging. Across all readers, confidence of cancer detection increased by 12.5% (p < 0.05), EPE by 14.7% (p < 0.05), SV invasion by 8.1% (p < 0.05), and LN metastasis by 2.5% (p < 0.05) using Wilcoxon signed rank test. PRINCIPAL CONCLUSIONS: Fusion overlay of high b-value DWI and T2WI increases sensitivity for detection of extraprostatic disease resulting in upstaging at the time of RP.

Hypusinated eIF5A is expressed in the pancreas and spleen of individuals with type 1 and type 2 diabetes.

The gene encoding eukaryotic initiation factor 5A (EIF5A) is found in diabetes-susceptibility loci in mouse and human. eIF5A is the only protein known to contain hypusine (hydroxyputrescine lysine), a polyamine-derived amino acid formed post-translationally in a reaction catalyzed by deoxyhypusine synthase (DHPS). Previous studies showed pharmacologic blockade of DHPS in type 1 diabetic NOD mice and type 2 diabetic db/db mice improved glucose tolerance and preserved beta cell mass, which suggests that hypusinated eIF5A (eIF5AHyp) may play a role in diabetes pathogenesis by direct action on the beta cells and/or altering the adaptive or innate immune responses. To translate these findings to human, we examined tissue from individuals with and without type 1 and type 2 diabetes to determine the expression of eIF5AHyp. We detected eIF5AHyp in beta cells, exocrine cells and immune cells; however, there was also unexpected enrichment of eIF5AHyp in pancreatic polypeptide-expressing PP cells. Interestingly, the presence of eIF5AHyp co-expressing PP cells was not enhanced with disease. These data identify new aspects of eIF5A biology and highlight the need to examine human tissue to understand disease.

Acute pancreatitis: an update on the revised Atlanta classification.

Acute pancreatitis (AP) is the most common gastrointestinal disease resulting in hospitalization in the United States with reports of over 270,000 hospitalizations and costs up to 2.6 billion dollars per year. AP is highly variable in disease course and outcome. Established in 1992, the original Atlanta classification system aimed to categorize the wide spectrum of AP by creating consensus-based terminology for AP types, severity, and complications. Though the original system standardized terminology, certain terms and definitions (i.e. pancreatic abscess) were unclear and often misused. The 2012 revised Atlanta classification (RAC) system updated terms, clarified definitions, and incorporated the medical community's improved understanding of the physiology of AP. The resulting RAC effectively defined the morphologic types of pancreatitis, provided a more standardized system for disease severity grading, further classified the local retroperitoneal complications, and established objective measures to describe this highly variable but common disease. This review provides an update on the recent literature evaluating the RAC, discusses both the strengths and shortcomings of the RAC system (including problematic interobserver agreement), and considers improvements for future classification systems.

Peroxisome Proliferator-activated Receptor-γ Activation Augments the ß-Cell Unfolded Protein Response and Rescues Early Glycemic Deterioration and ß Cell Death in Non-obese Diabetic Mice.

Type 1 diabetes is an autoimmune disorder that is characterized by a failure of the unfolded protein response in islet ß cells with subsequent endoplasmic reticulum stress and cellular death. Thiazolidinediones are insulin sensitizers that activate the nuclear receptor PPAR-γ and have been shown to partially ameliorate autoimmune type 1 diabetes in humans and non-obese diabetic (NOD) mice. We hypothesized that thiazolidinediones reduce ß cell stress and death independently of insulin sensitivity. To test this hypothesis, female NOD mice were administered pioglitazone during the pre-diabetic phase and assessed for insulin sensitivity and ß cell function relative to controls. Pioglitazone-treated mice showed identical weight gain, body fat distribution, and insulin sensitivity compared with controls. However, treated mice showed significantly improved glucose tolerance with enhanced serum insulin levels, reduced ß cell death, and increased ß cell mass. The effect of pioglitazone was independent of actions on T cells, as pancreatic lymph node T cell populations were unaltered and T cell proliferation was unaffected by pioglitazone. Isolated islets of treated mice showed a more robust unfolded protein response, with increases in Bip and ATF4 and reductions in spliced Xbp1 mRNA. The effect of pioglitazone appears to be a direct action on ß cells, as islets from mice treated with pioglitazone showed reductions in PPAR-γ (Ser-273) phosphorylation. Our results demonstrate that PPAR-γ activation directly improves ß cell function and survival in NOD mice by enhancing the unfolded protein response and suggest that blockade of PPAR-γ (Ser-273) phosphorylation may prevent type 1 diabetes.

Protective effects of polyamine depletion in mouse models of type 1 diabetes: implications for therapy.

The underlying pathophysiology of type 1 diabetes involves autoimmune-mediated islet inflammation, leading to dysfunction and death of insulin-secreting islet ß cells. Recent studies have shown that polyamines, which are essential for mRNA translation, cellular replication, and the formation of the hypusine modification of eIF5A may play an important role in the progression of cellular inflammation. To test a role for polyamines in type 1 diabetes pathogenesis, we administered the ornithine decarboxylase inhibitor difluoromethylornithine to two mouse models--the low-dose streptozotocin model and the NOD model--to deplete intracellular polyamines, and administered streptozotocin to a third model, which was haploinsufficient for the gene encoding the hypusination enzyme deoxyhypusine synthase. Subsequent development of diabetes and/or glucose intolerance was monitored. In the low-dose streptozotocin mouse model, continuous difluoromethylornithine administration dose-dependently reduced the incidence of hyperglycemia and led to the preservation of ß cell area, whereas in the NOD mouse model of autoimmune diabetes difluoromethylornithine reduced diabetes incidence by 50%, preserved ß cell area and insulin secretion, led to reductions in both islet inflammation and potentially diabetogenic Th17 cells in pancreatic lymph nodes. Difluoromethylornithine treatment reduced hypusinated eIF5A levels in both immune cells and islets. Animals haploinsufficient for the gene encoding deoxyhypusine synthase were partially protected from hyperglycemia induced by streptozotocin. Collectively, these studies suggest that interventions that interfere with polyamine biosynthesis and/or eIF5A hypusination may represent viable approaches in the treatment of diabetes.

Deoxyhypusine synthase promotes differentiation and proliferation of T helper type 1 (Th1) cells in autoimmune diabetes.

In type 1 diabetes, cytokines arising from immune cells cause islet ß cell dysfunction even before overt hyperglycemia. Deoxyhypusine synthase catalyzes the crucial hypusine modification of the factor eIF5A, which promotes the translation of a subset of mRNAs involved in cytokine responses. Here, we tested the hypothesis that deoxyhypusine synthase and, secondarily, hypusinated eIF5A contribute to the pathogenesis of type 1 diabetes using the non-obese diabetic (NOD) mouse model. Pre-diabetic NOD mice that received injections of the deoxyhypusine inhibitor N1-guanyl-1,7-diaminoheptane (GC7) demonstrated significantly improved glucose tolerance, more robust insulin secretion, and reduced insulitis compared with control animals. Analysis of tissues from treated mice revealed selective reductions in diabetogenic T helper type 1 (Th1) cells in the pancreatic lymph nodes, a primary site of antigen presentation. Isolated mouse CD90.2(+) splenocytes stimulated in vitro with anti-CD3/anti-CD28 and IL-2 to mimic autoimmune T cell activation exhibited proliferation and differentiation of CD4(+) T cell subsets (Th1, Th17, and Treg), but those treated with the deoxyhypusine synthase inhibitor GC7 showed a dose-dependent block in T cell proliferation with selective reduction in Th1 cells, similar to that observed in NOD mice. Inhibition of deoxyhypusine synthase blocked post-transcriptional expression of CD25, the high affinity IL-2 receptor α chain. Our results suggest a previously unrecognized role for deoxyhypusine synthase in promoting T cell proliferation and differentiation via regulation of CD25. Inhibition of deoxyhypusine synthase may provide a strategy for reducing diabetogenic Th1 cells and preserving ß cell function in type 1 diabetes.

Developmental analysis and influence of genetic background on the Lhx3 W227ter mouse model of combined pituitary hormone deficiency disease.

Combined pituitary hormone deficiency (CPHD) diseases result in severe outcomes for patients including short stature, developmental delays, and reproductive deficiencies. Little is known about their etiology, especially the developmental profiles and the influences of genetic background on disease progression. Animal models for CPHD provide valuable tools to investigate disease mechanisms and inform diagnostic and treatment protocols. Here we examined hormone production during pituitary development and the influence of genetic background on phenotypic severity in the Lhx3(W227ter/W227ter) mouse model. Lhx3(W227ter/W227ter) embryos have deficiencies of ACTH, α-glycoprotein subunit, GH, PRL, TSHß, and LHß during prenatal development. Furthermore, mutant mice have significant reduction in the critical pituitary transcriptional activator-1 (PIT1). Through breeding, the Lhx3(W227ter/W227ter) genotype was placed onto the 129/Sv and C57BL/6 backgrounds. Intriguingly, the genetic background significantly affected viability: whereas Lhx3(W227ter/W227ter) animals were found in the expected frequencies in C57BL/6, homozygous animals were not viable in the 129/Sv genetic environment. The hormone marker and PIT1 reductions observed in Lhx3(W227ter/W227ter) mice on a mixed background were also seen in the separate strains but in some cases were more severe in 129/Sv. To further characterize the molecular changes in diseased mice, we conducted a quantitative proteomic analysis of pituitary proteins. This showed significantly lower levels of PRL, pro-opiomelanocortin (ACTH), and α-glycoprotein subunit proteins in Lhx3(W227ter/W227ter) mice. Together, these data show that hormone deficiency disease is apparent in early prenatal stages in this CPHD model system. Furthermore, as is noted in human disease, genetic background significantly impacts the phenotypic outcome of these monogenic endocrine diseases.

Phosphatase of regenerating liver 2 (PRL2) is essential for placental development by down-regulating PTEN (Phosphatase and Tensin Homologue Deleted on Chromosome 10) and activating Akt protein.

The PRL (phosphatase of regenerating liver) phosphatases are implicated in the control of cell proliferation and invasion. Aberrant PRL expression is associated with progression and metastasis of multiple cancers. However, the specific in vivo function of the PRLs remains elusive. Here we show that deletion of PRL2, the most ubiquitously expressed PRL family member, leads to impaired placental development and retarded growth at both embryonic and adult stages. Ablation of PRL2 inactivates Akt and blocks glycogen cell proliferation, resulting in reduced spongiotrophoblast and decidual layers in the placenta. These structural defects cause placental hypotrophy and insufficiency, leading to fetal growth retardation. We demonstrate that the tumor suppressor PTEN is elevated in PRL2-deficient placenta. Biochemical analyses indicate that PRL2 promotes Akt activation by down-regulating PTEN through the proteasome pathway. This study provides the first evidence that PRL2 is required for extra-embryonic development and associates the oncogenic properties of PRL2 with its ability to negatively regulate PTEN, thereby activating the PI3K-Akt pathway.

Islet ß-cell endoplasmic reticulum stress precedes the onset of type 1 diabetes in the nonobese diabetic mouse model.

Type 1 diabetes is preceded by islet ß-cell dysfunction, but the mechanisms leading to ß-cell dysfunction have not been rigorously studied. Because immune cell infiltration occurs prior to overt diabetes, we hypothesized that activation of inflammatory cascades and appearance of endoplasmic reticulum (ER) stress in ß-cells contributes to insulin secretory defects. Prediabetic nonobese diabetic (NOD) mice and control diabetes-resistant NOD-SCID and CD1 strains were studied for metabolic control and islet function and gene regulation. Prediabetic NOD mice were relatively glucose intolerant and had defective insulin secretion with elevated proinsulin:insulin ratios compared with control strains. Isolated islets from NOD mice displayed age-dependent increases in parameters of ER stress, morphologic alterations in ER structure by electron microscopy, and activation of nuclear factor-κB (NF-κB) target genes. Upon exposure to a mixture of proinflammatory cytokines that mimics the microenvironment of type 1 diabetes, MIN6 ß-cells displayed evidence for polyribosomal runoff, a finding consistent with the translational initiation blockade characteristic of ER stress. We conclude that ß-cells of prediabetic NOD mice display dysfunction and overt ER stress that may be driven by NF-κB signaling, and strategies that attenuate pathways leading to ER stress may preserve ß-cell function in type 1 diabetes.

Model of pediatric pituitary hormone deficiency separates the endocrine and neural functions of the LHX3 transcription factor in vivo.

The etiology of most pediatric hormone deficiency diseases is poorly understood. Children with combined pituitary hormone deficiency (CPHD) have insufficient levels of multiple anterior pituitary hormones causing short stature, metabolic disease, pubertal failure, and often have associated nervous system symptoms. Mutations in developmental regulatory genes required for the specification of the hormone-secreting cell types of the pituitary gland underlie severe forms of CPHD. To better understand these diseases, we have created a unique mouse model of CPHD with a targeted knockin mutation (Lhx3 W227ter), which is a model for the human LHX3 W224ter disease. The LHX3 gene encodes a LIM-homeodomain transcription factor, which has essential roles in pituitary and nervous system development in mammals. The introduced premature termination codon results in deletion of the carboxyl terminal region of the LHX3 protein, which is critical for pituitary gene activation. Mice that lack all LHX3 function do not survive beyond birth. By contrast, the homozygous Lhx3 W227ter mice survive, but display marked dwarfism, thyroid disease, and female infertility. Importantly, the Lhx3 W227ter mice have no apparent nervous system deficits. The Lhx3 W227ter mouse model provides a unique array of hormone deficits and facilitates experimental approaches that are not feasible with human patients. These experiments demonstrate that the carboxyl terminus of the LHX3 transcription factor is not required for viability. More broadly, this study reveals that the in vivo actions of a transcription factor in different tissues are molecularly separable.

LHX3 and LHX4 transcription factors in pituitary development and disease.

The LHX3 and LHX4 LIM-homeodomain proteins are regulatory transcription factors that play overlapping but distinct functions during the establishment of the specialized cells of the mammalian pituitary gland and the nervous system. Recent studies have identified a variety of mutations in the LHX3 and LHX4 genes in patients with combined pituitary hormone deficiency diseases. These patients have complex and variable syndromes involving short stature, metabolic disorders, reproductive system deficits, and nervous system developmental abnormalities. The short stature secondary to growth hormone deficiency is a key feature of the disorders associated with these gene mutations and responds well to supplementation with recombinant growth hormone. Overall, the frequency of mutations in the LHX3 and LHX4 genes in patients with combined pituitary hormone deficiency is low. Mutations in other regulatory genes such as HESX1, PROP1, PIT1 / POU1F1, and GLI2 have been shown to be additional causes of pituitary hormone deficiency, but overall, the etiology of many cases of hypopituitarism is not understood. Further investigation is therefore required to identify other genes, both primary regulatory genes and those with modifier functions, which contribute to pituitary development and function.

Transgenic mice expressing LHX3 transcription factor isoforms in the pituitary: effects on the gonadotrope axis and sex-specific reproductive disease.

The LHX3 transcription factor plays critical roles in pituitary and nervous system development. Mutations in the human LHX3 gene cause severe hormone deficiency diseases. The gene produces two mRNAs which can be translated to three protein isoforms. The LHX3a protein contains a central region with LIM domains and a homeodomain, and a carboxyl terminus with the major transactivation domain. LHX3b is identical to LHX3a except that it has a different amino terminus. M2-LHX3 lacks the amino terminus and LIM domains of LHX3a/b. In vitro experiments have demonstrated these three proteins have different biochemical and gene regulatory properties. Here, to investigate the effects of overexpression of LHX3 in vivo, the alpha glycoprotein subunit (alphaGSU) promoter was used to produce LHX3a, LHX3b, and M2-LHX3 in the pituitary glands of transgenic mice. Alpha GSU-beta galactosidase animals were generated as controls. Male alphaGSU-LHX3a and alphaGSU-LHX3b mice are infertile and die at a young age as a result of complications associated with obstructive uropathy including uremia. These animals have a reduced number of pituitary gonadotrope cells, low circulating gonadotropins, and possible sex hormone imbalance. Female alphaGSU-LHX3a and alphaGSU-LHX3b transgenic mice are viable but have reduced fertility. By contrast, alphaGSU-M2-LHX3 mice and control mice expressing beta galactosidase are reproductively unaffected. These overexpression studies provide insights into the properties of LHX3 during pituitary development and highlight the importance of this factor in reproductive physiology.

Roles of the LHX3 and LHX4 LIM-homeodomain factors in pituitary development.

The LHX3 and LHX4 LIM-homeodomain transcription factors play essential roles in pituitary gland and nervous system development. Mutations in the genes encoding these regulatory proteins are associated with combined hormone deficiency diseases in humans and animal models. Patients with these diseases have complex syndromes involving short stature, and reproductive and metabolic disorders. Analyses of the features of these diseases and the biochemical properties of the LHX3 and LHX4 proteins will facilitate a better understanding of the molecular pathways that regulate the development of the specialized hormone-secreting cells of the mammalian anterior pituitary gland.

Regulation of the follicle-stimulating hormone beta gene by the LHX3 LIM-homeodomain transcription factor.

FSH is a critical hormone regulator of gonadal function that is secreted from the pituitary gonadotrope cell. Human patients and animal models with mutations in the LHX3 LIM-homeodomain transcription factor gene exhibit complex endocrine diseases, including reproductive disorders with loss of FSH. We demonstrate that in both heterologous and pituitary gonadotrope cells, specific LHX3 isoforms activate the FSH beta-subunit promoter, but not the proximal LHbeta promoter. The related LHX4 mammalian transcription factor can also induce FSHbeta promoter transcription, but the homologous Drosophila protein LIM3 cannot. The actions of LHX3 are specifically blocked by a dominant negative LHX3 protein containing a Kruppel-associated box domain. Six LHX3-binding sites were characterized within the FSHbeta promoter, including three within a proximal region that also mediates gene regulation by other transcription factors and activin. Mutations of the proximal binding sites demonstrate their importance for LHX3 induction of the FSHbeta promoter and basal promoter activity in gonadotrope cells. Using quantitative methods, we show that the responses of the FSHbeta promoter to activin do not require induction of the LHX3 gene. By comparative genomics using the human FSHbeta promoter, we demonstrate structural and functional conservation of promoter induction by LHX3. We conclude that the LHX3 LIM homeodomain transcription factor is involved in activation of the FSH beta-subunit gene in the pituitary gonadotrope cell.