Stimulation of the four isoforms of receptor tyrosine kinase ErbB4, but not ErbB1, confers cardiomyocyte hypertrophy.

Epidermal growth factor (EGF) receptors (ErbB1-ErbB4) promote cardiac development and growth, although the specific EGF ligands and receptor isoforms involved in growth/repair versus pathology remain undefined. We challenged ventricular cardiomyocytes with EGF-like ligands and observed that selective activation of ErbB4 (the receptor for neuregulin 1 [NRG1]), but not ErbB1 (the receptor for EGF, EGFR), stimulated hypertrophy. This lack of direct ErbB1-mediated hypertrophy occurred despite robust activation of extracellular-regulated kinase 1/2 (ERK) and protein kinase B.

Factors influencing cancer genetic somatic mutation test ordering by cancer physician.

Background: Clinical whole exome sequencing was introduced in an Australian centre in 2017, as an alternative to Sanger sequencing. We aimed to identify predictors of cancer physicians' somatic mutation test ordering behaviour.

Methods: A validated instrument assessed somatic mutation test ordering, genomic confidence, perceived utility of tumour molecular profiling, and percent of patients eligible for targeted therapy.

Genome-wide association study in Guillain-Barré syndrome.

Guillain-Barré syndrome (GBS) is considered to have an immune-mediated basis, but the genetic contribution to GBS is unclear. We conducted a GWAS involving 215 GBS patients and 1,105 healthy controls. No significant associations of individual SNPs or imputed HLA types were observed.

Crim1 is required for maintenance of the ocular lens epithelium.

The development and growth of the vertebrate ocular lens is dependent on the regulated proliferation of an anterior monolayer of epithelial cells, and their subsequent differentiation into elongate fiber cells. The growth factor rich ocular media that bathes the lens mediates these cellular processes, and their respective intracellular signaling pathways are in turn regulated to ensure that the proper lens architecture is maintained. Recent studies have proposed that Cysteine Rich Motor Neuron 1 (Crim1), a transmembrane protein involved in organogenesis of many tissues, might influence cell adhesion, polarity and proliferation in the lens by regulating integrin-signaling.

CRIM1 is necessary for coronary vascular endothelial cell development and homeostasis.

Endothelial cells form a critical component of the coronary vasculature, yet the factors regulating their development remain poorly defined. Here we reveal a novel role for the transmembrane protein CRIM1 in mediating cardiac endothelial cell development. In the absence of Crim1 in vivo, the coronary vasculature is malformed, the number of endothelial cells reduced, and the canonical BMP pathway dysregulated.

Crim1-, a regulator of developmental organogenesis.

The regulation of growth factor localization, availability and activity is critical during embryogenesis to ensure appropriate organogenesis. This process is regulated through the coordinated expression of growth factors and their cognate receptors, as well as via proteins that can bind, sequester or localize growth factors to distinct locations. One such protein is the transmembrane protein Crim1.

Distinct sites of renal fibrosis in Crim1 mutant mice arise from multiple cellular origins.

Crim1 is a transmembrane protein that regulates the bioavailability of growth factors such as VEGFA. Crim1(KST264)(/)(KST264) hypomorphic mice develop renal disease characterized by glomerular cysts and loss of endothelial integrity, progressing to peritubular and pericystic fibrosis. Peritubular capillary endothelial cells display morphological changes as well as detachment from the basement membrane.

Production of a mouse line with a conditional Crim1 mutant allele.

Crim1 is a developmentally expressed, transmembrane protein essential for normal embryonic development. We generated mice engineered to contain a Crim1 conditional null allele by flanking exons three and four of Crim1 with unidirectional LoxP sites. After crossing Crim1+/FLOX mice with a CMV-Cre line, a Crim1+/Δflox colony was established after germline transmission of the deleted allele.

Kidney development: two tales of tubulogenesis.

The mammalian kidney may well be one of the most complex organs of postnatal life. Each adult human kidney contains on average more than one million functional filtration units, the nephrons, residing within a specialized cellular interstitium. Each kidney also contains over 25 distinct cell types, each of which must be specifically aligned with respect to each other to ensure both normal development and ultimately, normal renal function.

Loss of renal microvascular integrity in postnatal Crim1 hypomorphic transgenic mice.

Crim1 is a cell-surface, transmembrane protein that binds to a variety of cystine knot-containing growth factors, including vascular endothelial growth factor A. In the developing renal glomerulus, Crim1 acts to tether vascular endothelial growth factor A to the podocyte cell surface, thus regulating its release to glomerular endothelial cells. The hypomorphic transgenic mouse (Crim1(KST264/KST264)) has glomerular cysts and severe glomerular vascular defects because of the lack of functional Crim1 in the glomerulus.

FGFR-1 is required by epicardium-derived cells for myocardial invasion and correct coronary vascular lineage differentiation.

Critical steps in coronary vascular formation include the epithelial-mesenchyme transition (EMT) that epicardial cells undergo to become sub-epicardial; the invasion of the myocardium; and the differentiation of coronary lineages. However, the factors controlling these processes are not completely understood. Epicardial and coronary vascular precursors migrate to the avascular heart tube during embryogenesis via the proepicardium (PE).

Crim1KST264/KST264 mice implicate Crim1 in the regulation of vascular endothelial growth factor-A activity during glomerular vascular development.

Crim1, a transmembrane cysteine-rich repeat-containing protein that is related to chordin, plays a role in the tethering of growth factors at the cell surface. Crim1 is expressed in the developing kidney; in parietal cells, podocytes, and mesangial cells of the glomerulus; and in pericytes that surround the arterial vasculature. A gene-trap mouse line with an insertion in the Crim1 gene (Crim1(KST264/KST264)) displayed perinatal lethality with defects in multiple organ systems.

Crim1KST264/KST264 mice display a disruption of the Crim1 gene resulting in perinatal lethality with defects in multiple organ systems.

Crim1 is a transmembrane protein, containing six vWF-C type cysteine-rich repeats, that tethers growth factors to the cell surface. A mouse line, KST264, generated in a LacZ insertion mutagenesis gene-trap screen, was examined to elucidate Crim1 function in development. We showed that Crim1(KST264/KST264) mice were not null for Crim1 due to the production of a shortened protein isoform.

Normal patterning of the coronary capillary plexus is dependent on the correct transmural gradient of FGF expression in the myocardium.

The formation of the coronary vessel system is vital for heart development, an essential step of which is the establishment of a capillary plexus that displays a density gradient across the myocardial wall, being higher on the epicardial than the endocardial side. This gradient in capillary plexus formation develops concurrently with transmural gradients of myocardium-derived growth factors, including FGFs. To test the role of the FGF expression gradient in patterning the nascent capillary plexus, an ectopic FGF-over-expressing site was created in the ventricular myocardial wall in the quail embryo via retroviral infection from E2-2.

A role for Tbx5 in proepicardial cell migration during cardiogenesis.

Transcriptional regulatory cascades during epicardial and coronary vascular development from proepicardial progenitor cells remain to be defined. We have used immunohistochemistry of human embryonic tissues to demonstrate that the TBX5 transcription factor is expressed not only in the myocardium, but also throughout the embryonic epicardium and coronary vasculature. TBX5 is not expressed in other human fetal vascular beds.

Hemodynamic-dependent patterning of endothelin converting enzyme 1 expression and differentiation of impulse-conducting Purkinje fibers in the embryonic heart.

Impulse-conducting Purkinje fibers differentiate from myocytes during embryogenesis. The conversion of contractile myocytes into conduction cells is induced by the stretch/pressure-induced factor, endothelin (ET). Active ET is produced via proteolytic processing from its precursor by ET-converting enzyme 1 (ECE1) and triggers signaling by binding to its receptors.

Epicardium is required for the full rate of myocyte proliferation and levels of expression of myocyte mitogenic factors FGF2 and its receptor, FGFR-1, but not for transmural myocardial patterning in the embryonic chick heart.

Proper heart development requires patterning across the myocardial wall. Early myocardial patterning is characterized by a transmural subdivision of the myocardium into an outer, highly mitotic, compact zone and an inner, trabecular zone with lower mitotic activity. We have shown previously that fibroblast growth factor receptor (FGFR) -mediated signaling is central to myocyte proliferation in the developing heart.

Induction and patterning of the Purkinje fibre network.

Impulse-conducting Purkinje cells differentiate from myocytes during embryogenesis. In the embryonic chicken heart, this conversion of contractile myocytes into conduction cells occurs subendocardially and periarterially. The unique sites of Purkinje fibre differentiation suggest that a shear stress-induced paracrine signal from the endocardium and arterial beds may induce adjacent myocytes to differentiate into conduction cells.

Induction and patterning of the cardiac conduction system.

The cardiac conduction system (CCS) is the component of the heart that initiates and maintains a rhythmic heartbeat. As the embryonic heart forms, the CCS must continue to develop and mature in a coordinated manner to ensure that proper pace making potential and distribution of action potential is maintained at all stages. This requires not only the formation of distinct and disparate components of the CCS, but the integration of these components into a functioning whole as the heart matures.