Biomedical subjects

K M Huelsman

Publications and source records attributed to K M Huelsman.

6 recordsLinked to original sources

PubMed2001

Is the P25L a "real" VHL mutation?

BACKGROUND: The von Hippel-Lindau (VHL) gene has two translational initiation sites separated by 53 codons. Both proteins have been detected in cells and have equivalent activity. A mutation in the first 53 codons of the open reading frame has no effect on the structure of the smaller protein. As expected, the vast majority of VHL mutations are downstream of the second initiation site and alter both proteins. However, several candidate mutations have been found in the first 53 codons, including a substitution of leucine for proline at position 25 (P25L) of the larger protein. METHODS AND RESULTS: DNA sequence analysis showed two VHL gene mutations, P25L and P86R, in an individual with a clinical diagnosis of VHL disease. Both mutations have been reported previously. P25L alters only the upstream protein, whereas P86R alters both VHL proteins. Based on the positions of the mutations, P86R is more likely to be pathogenically significant than the P25L mutation. A survey of anonymized DNAs for P25L, using allele-specific PCR, revealed that it is a variant with an allele frequency of approximately 0.5%. CONCLUSION: P25L is a rare variant of the VHL gene and cannot be considered a cause of VHL disease. However, this work does not prove that P25L is entirely innocuous.

Adolescent↗

PubMed1997

Surfactant protein A-deficient mice are susceptible to group B streptococcal infection.

To determine the role of surfactant protein A (SP-A) in host defense, the murine SP-A locus was targeted by homologous recombination to produce mice lacking SP-A. SP-A -/- and control mice were infected with group B streptococcus (GBS) by intratracheal instillation. Pulmonary infiltration 6 and 24 h following infection was more severe in SP-A -/- than in control mice, and was associated with increased numbers of GBS in lung homogenates. Dissemination of GBS to the spleen was observed more frequently in SP-A -/- mice. Pulmonary infiltration with macrophages was similar in both groups; however, the number of bacteria associated with alveolar macrophages was decreased in the SP-A-deficient mice. There was no detectable compensatory increase in surfactant protein D, the other known pulmonary collectin, in response to GBS instillation. SP-A plays an important role in vivo, enhancing clearance of GBS from the lung and inhibiting systemic dissemination of the organism.

Animals↗

PubMed1997

Postnatal lung function and morphology in transgenic mice expressing transforming growth factor-alpha.

Developmental changes in lung morphology and physiology during postnatal alveolarization were assessed in transgenic mice expressing transforming growth factor-alpha (TGF-alpha) in pulmonary type II cells under control of the surfactant protein C gene promoter. TGF-alpha transcripts were identified in respiratory epithelial cells at 1 day of age to adulthood. Enlargement of alveolar airspaces and fibrosis were detected as early as 1 week of age, and the increased airspace progressed with advancing age. Specific lung compliance was significantly increased in lungs of transgenic mice by 2 weeks of age and was associated with airflow obstruction. Chronic expression of TGF-alpha in the lungs of newborn transgenic mice caused remodeling of the developing lung during the period of postnatal alveolarization, resulting in markedly enlarged parenchymal airspace, pulmonary fibrosis, and physiological abnormalities including airway obstruction and increased lung compliance.

Animals↗

PubMed1996

Altered surfactant function and structure in SP-A gene targeted mice.

The surfactant protein A (SP-A) gene was disrupted by homologous recombination in embryonic stem cells that were used to generate homozygous SP-A-deficient mice. SP-A mRNA and protein were not detectable in the lungs of SP-A(-/-) mice, and perinatal survival of SP-A(-/-) mice was not altered compared with wild-type mice. Lung morphology, surfactant proteins B-D, lung tissue, alveolar phospholipid pool sizes and composition, and lung compliance in SP-A(-/-) mice were unaltered. At the highest concentration tested, surfactant from SP-A(-/-) mice produced the same surface tension as (+/+) mice. At lower concentrations, minimum surface tensions were higher for SP-A(-/-) mice. At the ultrastructural level, type II cell morphology was the same in SP-A(+/+) and (-/-) mice. While alveolar phospholipid pool sizes were unperturbed, tubular myelin figures were decreased in the lungs of SP-A(-/-) mice. A null mutation of the murine SP-A gene interferes with the formation of tubular myelin without detectably altering postnatal survival or pulmonary function.

Animals↗

PubMed1996

Reversal of lung lesions in transgenic transforming growth factor alpha mice by expression of mutant epidermal growth factor receptor.

Transgenic mice expressing transforming growth factor alpha (TGF-alpha) in type II cells under control of the lung-specific surfactant protein-C (SP-C) promoter develop pulmonary fibrosis and marked airspace hypoplasia. To identify cellular signaling mechanisms involved in lesion formation, we generated transgenic mice expressing a mutant epidermal growth factor receptor lacking a portion of the intracytoplasmic domain (EGF-R-M) under control of the human SP-C promoter. Transcripts of the SP-C-EGF-R-M transgene were detected in distal bronchiolar and type II cells by in situ hybridization. The morphology of lungs from the SP-C-EGF-R-M transgenic mice was normal. Lung fibrosis was not detectable and airspace hypoplasia was significantly corrected in bitransgenic mice derived by breeding SP-C-TGF-alpha and SP-C-EGF-R-M mice. Correction of lung pathology in the bitransgenic mice occurred without altering the level of hTGF-alpha mRNA. To further demonstrate that reversal of TGF-alpha lesions required signaling through the EGF-R, SP-C-TGF-alpha transgenic mice were bred to mice homozygous for the wa-2 mutation which encodes a mutated EGF-R. TGF-alpha-induced lesions were reversed in homozygous wa-2 mice. Amelioration of TGF-alpha-dependent pulmonary lesions in SP-C-EGF-R-M mice or wa-2/wa-2 mice supports the concept that autocrine and paracrine signaling mediate fibrosis and airspace remodeling caused by TGF-alpha.

Animals↗

PubMed1995

Lung cell-specific expression of the murine surfactant protein A (SP-A) gene is mediated by interactions between the SP-A promoter and thyroid transcription factor-1.

Cis-acting elements determining lung epithelial cell-selective transcription of the murine surfactant protein A (SP-A) gene were identified between nucleotide positions -255 and -57. This region of the murine SP-A gene contained nucleotide sequences consistent with thyroid transcription factor-1 (TTF-1) binding motifs. An SP-A-CAT plasmid containing the TTF-1 binding sites was transcriptionally active in mouse lung epithelial (MLE-15) cells but not in HeLa, 3T3, or H441 cells. However, transcription of the SP-A-CAT construct was activated after cotransfection of HeLa cells with a vector expressing recombinant TTF-1, pCMV-TTF-1. Recombinant TTF-1 homeodomain protein bound to four distinct binding sites located between nucleotides -166 to -117 [corrected]. Proteins in nuclear extracts of MLE-15 cells bound TTF-1 binding sites and were supershifted by TTF-1 antibody. Mutations of three of the TTF-1 binding sites in this region reduced expression of the SP-A-CAT construct in transfected MLE-15 cells and reduced transactivation in HeLa cells. TTF-1 interacts with complex protein/DNA binding sites located in the 5'-flanking region of the murine SP-A gene enhancing lung epithelial cell-specific expression in vitro.

Animals↗