Aggressive papillomas and soft tissue sarcomas in<i>AID-Cre-YFP Kras^G12D Arf^−/−</i> mice.

<p><b>A)</b> Gross appearance of progressive tumors affecting an <i>AID-Cre-YFP Kras^G12D Arf ^−/−</i> mouse at 13 weeks of age. Tumors progressed rapidly from smaller papillomas on the ventral neck. <b>B)</b> Control <i>AID-Cre-YFP Arf ^−/−</i> control mouse at 13 weeks appears normal. Hematoxalin & eosin stains of <b>C)</b> spleen section from <i>AID-Cre-YFP Kras^G12D Arf ^−/−</i> shows disruption of splenic architecture by inflammatory cells; <b>D)</b> spleen section from <i>AID-Cre-YFP Arf ^−/−</i> control appears normal; and <b>E)</b> section of subcutaneous sarcoma from <i>AID-Cre-YFP Kras^G12D Arf ^−/−</i> at 13 weeks shows spindle shaped cells consistent with soft tissue sarcoma. Original magnification, x10 (spleen); x40 (sarcoma). Scale bar: 200 um (spleen); 50 um (sarcoma). Tumor development was uniform in <i>AID-Cre-YFP Kras^G12D Arf ^−/−</i> mice and did not require any tumor-promoting treatment. Representative images are shown.</p

New insights into the pathogenesis of autosomal-dominant cutis laxa with report of five ELN mutations

Autosomal dominant cutis laxa (ADCL) is characterized by a typical facial appearance and generalized loose skin folds, occasionally associated with aortic root dilatation and emphysema. We sequenced exons 28–34 of the ELN gene in 5 probands with ADCL features and found 5 de novo heterozygous mutations: c.2296_2299dupGCAG (CL-1), c.2333delC (CL-2), c.2137delG (CL-3), c.2262delA (monozygotic twin CL-4 and CL-5) and c.2124del25 (CL-6). Four probands (CL-1, -2, -3, -6) presented with progressive aortic root dilatation. CL-2 and CL-3 also had bicuspid aortic valves. CL-2 presented with severe emphysema. Electron microscopy revealed elastic fiber fragmentation and diminished dermal elastin deposition. RT-PCR studies showed stable mutant mRNA in all patients. Exon 32 skipping explains a milder phenotype in patients with exon 32 mutations. Mutant protein expression in fibroblast cultures impaired deposition of tropoelastin onto microfibril-containing fibers, and enhanced tropoelastin coacervation and globule formation leading to lower amounts of mature, insoluble elastin. Mutation-specific effects also included endoplasmic reticulum stress and increased apoptosis. Increased pSMAD2 staining in ADCL fibroblasts indicated enhanced transforming growth factor beta (TGFβ) signaling. We conclude that ADCL is a systemic disease with cardiovascular and pulmonary complications, associated with increased TGFβ signaling and mutation-specific differences in endoplasmic reticulum stress and apoptosis

Gross appearance of cutaneous papillomas in<i>AID-Cre-YFP Kras^G12</i>^D mice is enhanced by tumor-promoting treatments.

<p><b>A</b>) By 3 weeks of age, <i>AID-Cre-YFP Kras^G12</i>^D mice uniformly have hair loss and a single papilloma localized to the ventral neck; <b>B</b>) control <i>Kras^G12</i>^D mouse shows normal hair pattern and no papilloma; <b>C</b>) By 17 weeks, <i>AID-Cre-YFP Kras^G12</i>^D mice given radiation and vitamin D deficient chow (RV) had numerous fungating papillomas and more hair loss at the same site on the ventral neck; <b>D</b>) <i>AID-Cre-YFP Kras^G12</i>^D mice without tumor-promoting treatments also had progressive papillomas but much fewer and with less hair loss associated; <b>E</b>) <i>AID-Cre-YFP Kras^G12</i>^D+RV mice aged to 26 weeks showed confluent fungating and ulcerated masses at the ventral neck with spread to paws; <b>F</b>) age-matched control <i>Kras^G12</i>^D+RV mouse shows no similar signs.</p

Schematic of alleles used in generating transgenic mice.

<p><b>A)</b> Floxed <i>Kras</i> allele with exons 0, 1, and 2, under the endogenous Kras locus. Asterisk represents G12D mutation in exon 1. <b>B)</b> Excision of the stop cassette of the <i>Kras</i> allele by Cre recombinase allows the G12D mutation to activate. <b>C)</b> The Cre-coding sequence is knocked in downstream of the last coding exon of the Cγ1 locus. Expression of Cre recombinase is induced by transcription of the Ig γ1 constant region. <b>D)</b> After the floxed neomycin gene is deleted by Cre-mediation, the YFP is expressed alongside AID-expressing B cells.</p

Mutations in LTBP4 Cause a Syndrome of Impaired Pulmonary, Gastrointestinal, Genitourinary, Musculoskeletal, and Dermal Development

We report recessive mutations in the gene for the latent transforming growth factor-β binding protein 4 (LTBP4) in four unrelated patients with a human syndrome disrupting pulmonary, gastrointestinal, urinary, musculoskeletal, craniofacial, and dermal development. All patients had severe respiratory distress, with cystic and atelectatic changes in the lungs complicated by tracheomalacia and diaphragmatic hernia. Three of the four patients died of respiratory failure. Cardiovascular lesions were mild, limited to pulmonary artery stenosis and patent foramen ovale. Gastrointestinal malformations included diverticulosis, enlargement, tortuosity, and stenosis at various levels of the intestinal tract. The urinary tract was affected by diverticulosis and hydronephrosis. Joint laxity and low muscle tone contributed to musculoskeletal problems compounded by postnatal growth delay. Craniofacial features included microretrognathia, flat midface, receding forehead, and wide fontanelles. All patients had cutis laxa. Four of the five identified LTBP4 mutations led to premature termination of translation and destabilization of the LTBP4 mRNA. Impaired synthesis and lack of deposition of LTBP4 into the extracellular matrix (ECM) caused increased transforming growth factor-β (TGF-β) activity in cultured fibroblasts and defective elastic fiber assembly in all tissues affected by the disease. These molecular defects were associated with blocked alveolarization and airway collapse in the lung. Our results show that coupling of TGF-β signaling and ECM assembly is essential for proper development and is achieved in multiple human organ systems by multifunctional proteins such as LTBP4