Cell cycle-related kinase regulates mammalian eye development through positive and negative regulation of the Hedgehog pathway

A Novel Missense Variant in LHX4 in Three Children with Multiple Pituitary Hormone Deficiency Belonging to Two Unrelated Families and Contribution of Additional GLI2 and IGFR1 Variant

BACKGROUND

Multiple genes can disrupt hypothalamic-pituitary axis development, causing multiple pituitary hormone deficiencies (MPHD). Despite advances in next-generation sequencing (NGS) identifying over 30 key genes, 85% of cases remain unsolved, indicating complex genotype-phenotype correlations and variable inheritance patterns.

OBJECTIVE

This study aimed to identify the MPHD genetics in three probands from two unrelated families.

METHODS

Family A had one affected child, while Family B had two affected siblings. All probands exhibited poor growth since birth, and family B's probands were born small for gestational age. Growth hormone deficiency was confirmed in all subjects. Family B's probands responded poorly to growth hormone treatment compared to the first patient. Furthermore, Family A's proband and Family B's younger sibling developed central hypothyroidism, while Family B's older sibling presented hypogonadotropic hypogonadism. Brain magnetic resonance imaging (MRI) revealed pituitary hypoplasia, ectopic posterior pituitary gland, and small sella turcica in all probands. Patients and their available relatives underwent NGS.

RESULTS

NGS identified the same novel and likely pathogenic LHX4 variant (c.481C>G) in all probands despite the families being unrelated. Additionally, Family A's proband carried a GLI2 variant (c.2105C>A), and Family B's probands carried an IGF1R variant (c.166G>A), both interpreted as being of uncertain significance.

CONCLUSIONS

This study confirms that heterozygous pathogenic variants of LHX4 can cause MPHD associated with a specific neuroradiological triad of abnormalities despite incomplete penetrance and variable phenotype. Moreover, the co-occurrence of the other two gene variants was debated. The IGF1R variant could explain the unusually poor response to growth hormone therapy in Family B, suggesting an oligogenic mechanism underlying the phenotype.

Cyclin-dependent protein kinases and cell cycle regulation in biology and disease

Cyclin Dependent Kinases (CDKs) are closely connected to the regulation of cell cycle progression, having been first identified as the kinases able to drive cell division. In reality, the human genome contains 20 different CDKs, which can be divided in at least three different sub-family with different functions, mechanisms of regulation, expression patterns and subcellular localization. Most of these kinases play fundamental roles the normal physiology of eucaryotic cells; therefore, their deregulation is associated with the onset and/or progression of multiple human disease including but not limited to neoplastic and neurodegenerative conditions. Here, we describe the functions of CDKs, categorized into the three main functional groups in which they are classified, highlighting the most relevant pathways that drive their expression and functions. We then discuss the potential roles and deregulation of CDKs in human pathologies, with a particular focus on cancer, the human disease in which CDKs have been most extensively studied and explored as therapeutic targets. Finally, we discuss how CDKs inhibitors have become standard therapies in selected human cancers and propose novel ways of investigation to export their targeting from cancer to other relevant chronic diseases. We hope that the effort we made in collecting all available information on both the prominent and lesser-known CDK family members will help in identify and develop novel areas of research to improve the lives of patients affected by debilitating chronic diseases.

CARD9 promotes cholangiocarcinoma by regulating the IL-17A/Hedgehog and the THEM4/AKT/mTOR signaling pathways

Cholangiocarcinoma (CCA) is a highly lethal malignant tumor originating from the bile duct, and its underlying mechanisms are not fully understood. In order to identify key genes in CCA, we downloaded gene expression data from public GSE76297, GSE26566 and TCGA-CHOL datasets. CARD9 was selected as a CCA-related gene from the datasets. Its expression was identified in the CCA tissues via PCR, western blot and immunohistochemistry assays. The loss-and-gain function assay of CARD9 was conducted in CCA cell lines (QBC939 and RBE) and nude mice. This study found a significant upregulation of CARD9 in CCA tissues, which is associated with poor prognosis in patients. Overexpression of CARD9 promotes proliferation and invasion of QBC939 and RBE cells, enhances the growth and development in CCA mouse models, and reduces sensitivity to chemotherapy drugs for CCA. Mechanistically, CARD9 activates the NF-κB and NLRP3 inflammatory signaling pathways, induces excessive release of various inflammatory factors, and triggers a cascade reaction of interleukin-17 (IL-17A). IL-17A promotes the stability of IHH mRNA by regulating HuR, enhances IHH transcription, and activates the Hedgehog signaling pathway to accelerate the progression of CCA. In addition, CARD9 promotes proliferation and invasion of CCA cells by interacting with THEM4, thereby facilitating AKT and mTOR phosphorylation, and accelerating the progression of CCA. Overall, these data suggest that CARD9 is involved in the progression of CCA by regulating the IL-17A/Hedgehog and the THEM4/AKT/mTOR signaling pathways. Therefore, CARD9 may serve as a novel therapeutic target for CCA treatment.

Construction and Identification of a Novel Mice Model of Microphthalmia

Purpose

Microphthalmia is a rare developmental eye disease that affects 1 in 7000 births. Currently, there is no cure for this condition. This study aimed to construct a stable mouse model of microphthalmia, thus providing a new tool for the study of the etiology of microphthalmia.

Methods

The Hedgehog signaling pathway plays a crucial role in eye development. One of the key mechanisms of the Sonic Hedgehog signaling is the strong transcriptional activation ability of GLI3, a major mediator of this pathway. This study used CRISPR/Cas9 system to construct a novel TgGli3Ki/Ki lens-specific over-expression mouse line. To identify the ocular characteristics of this line, quantitative PCR, Western blot, hematoxylin and eosin staining, immunofluorescent staining, and RNA-seq were performed on the ocular tissues of this line and normal mice.

Results

The TgGli3Ki/Ki lens-specific over-expression mouse model exhibits the ocular phenotype of microphthalmia. In the TgGli3Ki/Ki mouse, Gli3 is over-expressed in the lens, and the size of the eyeball and lens is significantly smaller than the normal one. RNA-seq analysis using the lens and the retina samples from TgGli3Ki/Ki and normal mice indicates that the phototransduction pathway is ectopically activated in the lens. Immunofluorescent staining of the lens samples confirmed this activation.

Conclusions

The TgGli3Ki/Ki mouse model consistently manifests the stereotypical microphthalmia phenotype across generations, making it an excellent tool for studying this severe eye disease.

Translational Relevance

This study developed a novel animal model to facilitate clinical research on microphthalmia.

Role of ciliopathy protein TMEM107 in eye development: insights from a mouse model and retinal organoid

Primary cilia are cellular surface projections enriched in receptors and signaling molecules, acting as signaling hubs that respond to stimuli. Malfunctions in primary cilia have been linked to human diseases, including retinopathies and ocular defects. Here, we focus on TMEM107, a protein localized to the transition zone of primary cilia. TMEM107 mutations were found in patients with Joubert and Meckel-Gruber syndromes. A mouse model lacking Tmem107 exhibited eye defects such as anophthalmia and microphthalmia, affecting retina differentiation. Tmem107 expression during prenatal mouse development correlated with phenotype occurrence, with enhanced expression in differentiating retina and optic stalk. TMEM107 deficiency in retinal organoids resulted in the loss of primary cilia, down-regulation of retina-specific genes, and cyst formation. Knocking out TMEM107 in human ARPE-19 cells prevented primary cilia formation and impaired response to Smoothened agonist treatment because of ectopic activation of the SHH pathway. Our data suggest TMEM107 plays a crucial role in early vertebrate eye development and ciliogenesis in the differentiating retina.

Post-translational modification enzymes as key regulators of ciliary protein trafficking

Primary cilia are evolutionarily conserved microtubule-based organelles that protrude from the surface of almost all cell types and decode a variety of extracellular stimuli. Ciliary dysfunction causes human diseases named ciliopathies, which span a wide range of symptoms, such as developmental and sensory abnormalities. The assembly, disassembly, maintenance and function of cilia rely on protein transport systems including intraflagellar transport (IFT) and lipidated protein intraflagellar targeting (LIFT). IFT is coordinated by three multisubunit protein complexes with molecular motors along the ciliary axoneme, while LIFT is mediated by specific chaperones that directly recognize lipid chains. Recently, it has become clear that several post-translational modification enzymes play crucial roles in the regulation of IFT and LIFT. Here, we review our current understanding of the roles of these post-translational modification enzymes in the regulation of ciliary protein trafficking as well as their regulatory mechanisms, physiological significance and involvement in human diseases.

Cell cycle-related kinase reprograms the liver immune microenvironment to promote cancer metastasis

The liver is an immunologically tolerant organ and a common metastatic site of multiple cancer types. Although a role for cancer cell invasion programs has been well characterized, whether and how liver-intrinsic factors drive metastatic spread is incompletely understood. Here, we show that aberrantly activated hepatocyte-intrinsic cell cycle-related kinase (CCRK) signaling in chronic liver diseases is critical for cancer metastasis by reprogramming an immunosuppressive microenvironment. Using an inducible liver-specific transgenic model, we found that CCRK overexpression dramatically increased both B16F10 melanoma and MC38 colorectal cancer (CRC) metastasis to the liver, which was highly infiltrated by polymorphonuclear-myeloid-derived suppressor cells (PMN-MDSCs) and lacking natural killer T (NKT) cells. Depletion of PMN-MDSCs in CCRK transgenic mice restored NKT cell levels and their interferon gamma production and reduced liver metastasis to 2.7% and 0.7% (metastatic tumor weights) in the melanoma and CRC models, respectively. Mechanistically, CCRK activated nuclear factor-kappa B (NF-κB) signaling to increase the PMN-MDSC-trafficking chemokine C-X-C motif ligand 1 (CXCL1), which was positively correlated with liver-infiltrating PMN-MDSC levels in CCRK transgenic mice. Accordingly, CRC liver metastasis patients exhibited hyperactivation of hepatic CCRK/NF-κB/CXCL1 signaling, which was associated with accumulation of PMN-MDSCs and paucity of NKT cells compared to healthy liver transplantation donors. In summary, this study demonstrates that immunosuppressive reprogramming by hepatic CCRK signaling undermines antimetastatic immunosurveillance. Our findings offer new mechanistic insights and therapeutic targets for liver metastasis intervention.

Loss-of-Function Variants in TBC1D32 Underlie Syndromic Hypopituitarism

CONTEXT

Congenital pituitary hormone deficiencies with syndromic phenotypes and/or familial occurrence suggest genetic hypopituitarism; however, in many such patients the underlying molecular basis of the disease remains unknown.

OBJECTIVE

To describe patients with syndromic hypopituitarism due to biallelic loss-of-function variants in TBC1D32, a gene implicated in Sonic Hedgehog (Shh) signaling.

SETTING

Referral center.

PATIENTS

A Finnish family of 2 siblings with panhypopituitarism, absent anterior pituitary, and mild craniofacial dysmorphism, and a Pakistani family with a proband with growth hormone deficiency, anterior pituitary hypoplasia, and developmental delay.

INTERVENTIONS

The patients were investigated by whole genome sequencing. Expression profiling of TBC1D32 in human fetal brain was performed through in situ hybridization. Stable and dynamic protein-protein interaction partners of TBC1D32 were investigated in HEK cells followed by mass spectrometry analyses.

MAIN OUTCOME MEASURES

Genetic and phenotypic features of patients with biallelic loss-of-function mutations in TBC1D32.

RESULTS

The Finnish patients harboured compound heterozygous loss-of-function variants (c.1165_1166dup p.(Gln390Phefs*32) and c.2151del p.(Lys717Asnfs*29)) in TBC1D32; the Pakistani proband carried a known pathogenic homozygous TBC1D32 splice-site variant c.1372 + 1G > A p.(Arg411_Gly458del), as did a fetus with a cleft lip and partial intestinal malrotation from a terminated pregnancy within the same pedigree. TBC1D32 was expressed in the developing hypothalamus, Rathke's pouch, and areas of the hindbrain. TBC1D32 interacted with proteins implicated in cilium assembly, Shh signaling, and brain development.

CONCLUSIONS

Biallelic TBC1D32 variants underlie syndromic hypopituitarism, and the underlying mechanism may be via disrupted Shh signaling.

Patterning the Vertebrate Retina with Morphogenetic Signaling Pathways

The primordium of the vertebrate eye is composed of a pseudostratified and apparently homogeneous neuroepithelium, which folds inward to generate a bilayered optic cup. During these early morphogenetic events, the optic vesicle is patterned along three different axes-proximo-distal, dorso-ventral, and naso-temporal-and three major domains: the neural retina, the retinal pigment epithelium (RPE), and the optic stalk. These fundamental steps that enable the subsequent development of a functional eye, entail the precise coordination among genetic programs. These programs are driven by the interplay of signaling pathways and transcription factors, which progressively dictate how each tissue should evolve. Here, we discuss the contribution of the Hh, Wnt, FGF, and BMP signaling pathways to the early patterning of the retina. Comparative studies in different vertebrate species have shown that their morphogenetic activity is repetitively used to orchestrate the progressive specification of the eye with evolutionary conserved mechanisms that have been adapted to match the specific need of a given species.

GLI3 repressor but not GLI3 activator is essential for mouse eye patterning and morphogenesis

Since 1967, it is known that the loss of GLI3 causes very severe defects in murine eye development. GLI3 is able to act as a transcriptional activator (GLI3-A) or as a transcriptional repressor (GLI3-R). Soon after the discovery of these GLI3 isoforms, the question arose which of the different isoforms is involved in eye formation - GLI3-A, GLI3-R or even both. For several years, this question remained elusive. By analysing the eye morphogenesis of Gli3^XtJ/XtJ mouse embryos that lack GLI3-A and GLI3-R and of Gli3^Δ699/Δ699 mouse embryos in which only GLI3-A is missing, we revealed that GLI3-A is dispensable in vertebrate eye formation. Remarkably, our study shows that GLI3-R is sufficient for the creation of morphologically normal eyes although the molecular setup deviates substantially from normality. In depth-investigations elucidated that GLI3-R controls numerous key players in eye development and governs lens and retina development at least partially via regulating WNT/β-CATENIN signalling.

The hedgehog pathway and ocular developmental anomalies

Mutations in effectors of the hedgehog signaling pathway are responsible for a wide variety of ocular developmental anomalies. These range from massive malformations of the brain and ocular primordia, not always compatible with postnatal life, to subtle but damaging functional effects on specific eye components. This review will concentrate on the effects and effectors of the major vertebrate hedgehog ligand for eye and brain formation, Sonic hedgehog (SHH), in tissues that constitute the eye directly and also in those tissues that exert indirect influence on eye formation. After a brief overview of human eye development, the many roles of the SHH signaling pathway during both early and later morphogenetic processes in the brain and then eye and periocular primordia will be evoked. Some of the unique molecular biology of this pathway in vertebrates, particularly ciliary signal transduction, will also be broached within this developmental cellular context.