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B C Powell

Publications and source records attributed to B C Powell.

At least 37 records · Page 2Linked to original sources
PubMed1994

Characterization of a hair (wool) keratin intermediate filament gene domain.

In epithelial differentiation keratin intermediate filament genes are expressed in multifarious tissue-specific and stage-specific patterns. Pairs of type I and type II intermediate filament genes, belonging to multigene families, are coordinately regulated, and 4-5 genes of each type are expressed in the hair follicle. Accumulating chromosomal mapping data points to a major locus for each intermediate filament multigene family on separate chromosomes. In this report we describe the isolation of a sheep hair keratin cosmid by chromosome walking that overlaps two previously described cosmids and establishes a continuous 100-kb segment of cloned DNA containing three hair and three hair-like type II intermediate filament keratin genes. A new hair keratin type II intermediate filament gene, KRT2.11, is located in the middle of the cluster, and partial sequence data reveal a striking conservation of its predicted N-terminal region with other sheep hair keratin type II intermediate filament proteins. Expression analyses demonstrate the presence of a 2.4-kb KRT2.11 transcript in wool follicle RNA and show that expression occurs in the follicle cortical keratinocytes above the dermal papilla. The three hair genes are clustered within about 40 kb and flanked by hair-like genes that are not expressed in the hair follicle, thereby demarcating a hair keratin gene domain.

Amino Acid Sequence↗
PubMed1994

Dietary cysteine regulates the levels of mRNAs encoding a family of cysteine-rich proteins of wool.

The abomasal or intravenous infusion of sulphur-containing amino acids such as cysteine or methionine into sheep on low-quality diets increases the sulphur content of the wool by increasing the synthesis of proteins containing a cysteine content of approximately 30 mol %. To investigate the molecular and cellular basis of this nutritional effect, quantitative analyses of wool keratin mRNA and protein levels, and follicle cortical cell type, were undertaken in sheep intravenously infused with cysteine. Northern blot analyses revealed that the mRNA levels of one gene family encoding cysteine-rich keratin-associated proteins (KAP4 family) expressed in the wool follicle cortex, increased approximately 5-6 times. Furthermore, the response was rapid as the mRNA levels increased approximately 3.5 times after 1 d of the cysteine infusion and, by 1 d post-infusion, they had fallen, approaching their basal level. No changes in the mRNA levels encoding the intermediate filament or the other keratin-associated protein families of lower cysteine content were observed. Concomitantly, two-dimensional polyacrylamide gel electrophoresis analysis of wool proteins showed a striking increase in the abundance of a group of cysteine-rich keratin-associated proteins in the wool by the end of the infusion period, returning to basal levels by 3 weeks later. At the cellular level, KAP4 expression was localized to the follicle paracortical cells, and the proportion of paracortical cells and the extent of KAP4 expression paralleled the changes in the cysteine infusion status of the sheep.

Amino Acid Sequence↗
PubMed1994

Differential expression of genes encoding a cysteine-rich keratin family in the hair cuticle.

In the hair follicle the cuticle develops as a thin layer of cells between the hair shaft cortex and the inner root sheath. Once the cuticle cells begin to differentiate they accumulate cysteine-rich granules in their cytoplasm but the identity of their constituent proteins has remained largely an enigma. In this report we show differential expression of a family of genes encoding cysteine-rich, glycine-rich keratins in the cuticle. Two clones of the sheep KAP5 gene family were isolated: the KAP5.4 cDNA encodes a protein of 190 amino acids (M(r) = 16,936) containing 32 mol% cysteine, 26 mol% glycine and the partial KAP5.5 cDNA encodes a protein of at least 197 amino acids (M(r) > or = 17,474) containing 29 mol% cysteine, 28 mol% glycine. The predicted amino acid sequences of the KAP5 family show extensive sequence conservation and all the proteins are composed almost entirely of cysteine-rich and glycine-rich repeats. Each KAP5 gene produces an approximately 1.5-kb mRNA species but the KAP5.4 and KAP5.5 mRNA levels appear to be severalfold greater than the KAP5.1 mRNA. Comparative tissue in situ hybridizations reveal a positive correlation between the onset of expression and follicle depth. For a given KAP5 gene two widely different cuticle expression patterns were noted amongst the follicle populations, and on the basis of follicle bulb cell kinetics they are consistent with expression in either sheep primary or secondary follicle types.

Amino Acid Sequence↗
PubMed1993

Sequence, expression, and evolutionary conservation of a gene encoding a glycine/tyrosine-rich keratin-associated protein of hair.

In hair differentiation several families of keratin proteins with distinctive amino acid compositions are produced. To study the role and regulation of one of these families, the glycine/tyrosine-rich keratin-associated proteins encoded by the KAP6 gene family, a partial wool follicle cDNA clone encoding a sheep KAP6 protein was sequenced and the corresponding gene isolated from a sheep cosmid library. The KAP6.1 gene encodes a basic protein of 82 amino acids (M(r) = 8,296) with a combined glycine and tyrosine content of approximately 60 mol%. There are several KAP6 genes in the sheep genome, all located within a 1,050-kilobase SfiI fragment. Northern blot analysis demonstrated that at least one member of the KAP6 family is expressed in the wool follicle. A rabbit KAP6 gene was isolated and its sequence and expression patterns were compared with the sheep gene. The sheep and rabbit genes have a nucleotide sequence identity of 89%, suggesting that they are equivalent genes and indicating strong selection pressure during evolution. Both genes contain several conserved sequence motifs of 7-9 nucleotides in their 5'-flanking regions that may be involved in the regulation of their expression. Localization of KAP6 mRNAs in sheep wool and rabbit hair follicles by in situ hybridization suggests that the genes are expressed in the cells of the hair shaft cortex in varying expression patterns. KAP6 expression starts relatively late in hair follicle differentiation, and the proportion of hair cortical cells that express it may change from follicle to follicle.

Amino Acid Sequence↗
PubMed1993

Organization and expression of hair follicle genes.

Several families of proteins are expressed in the growth of hair and an estimated 50-100 proteins constitute the final hair fiber. The cumbersome nomenclature for naming these different proteins has led to a proposal to modify that which is currently used for epidermal keratins. Investigations of the organization of hair genes indicate that the members of each family are clustered in the genome and their expression could be under some general control. Interestingly, the protein called trichohyalin, markedly distinct from the hair proteins, is produced in the inner root sheath cells and the gene for it has been found to be located at the same human chromosome locus as the genes for profilaggrin, involucrin, and loricrin. A mainstream objective is to identify controls responsible for the production in the hair cortex of keratin intermediate filaments (IFs) and two large groups of keratin-associated proteins (KAPs) rich in the amino acids cysteine or glycine/tyrosine. A specific family of cysteine-rich proteins is expressed in the hair cuticle. Comparisons of promoter regions of IF genes and KAP genes, including a recently characterized gene for a glycine/tyrosine-rich protein, have revealed putative hair-specific motifs in addition to known elements that regulate gene expression. In the sheep, the patterns of expression in hair differentiation are particularly interesting insofar as there are distinct segments of para- and orthocortical type cells that have significantly different pathways of expression. The testing of candidate hair-specific regulatory sequences by mouse transgenesis has produced several interesting hair phenotypes. Transgenic sheep over-expressing keratin genes but showing no hair growth change have been obtained and compared with the equivalent transgenic hair-loss mice. Studies of the effects of amino acid supply on the rate of hair growth have demonstrated that with cysteine supplementation of sheep a perturbation occurs in which there is a markedly increased level of only one type of mRNA and the ration of para- to orthocortical cells is increased. A molecular explanation of this phenomenon is being sought.

Animals↗
PubMed1993

Complete sequence of a hair-like intermediate filament type II keratin gene.

The Intermediate Filament (IF) superfamily comprises several multigene families, of which the two keratin families are the largest. The keratin IF genes are expressed in epithelial tissues in differentiation-specific patterns and recently we reported the sequence and expression of a hair IF type II keratin gene (KRT2.9). Two related genes were present in the cosmid containing KRT2.9 and we have now sequenced one of them and found that it encodes a hair-like IF type II protein (KRT2.13). However, KRT2.13 is not expressed in the hair follicle. Interestingly there is significant sequence homology between introns 1, 5 and 6 of KRT2.13 and KRT2.9 to suggest gene conversion of these regions or possibly conservation of functional sequences.

Amino Acid Sequence↗
PubMed1992

Localization by in situ hybridization of a type I keratin intermediate filament gene (Krt-1.14) to band D of mouse chromosome 11.

A probe from the 3' noncoding region of a murine type I keratin intermediate filament (IF) gene (Krt-1.14) localizes to band D of murine Chromosome 11 using in situ hybridization. This localization provides a physical confirmation of the assignment of the type I keratin genes by linkage analysis in the mouse. It also demonstrates that the Krt-1.14 genes are at a single locality in the mouse in contrast to the two locations on the short and long arms of chromosome 17 in humans.

Animals↗
PubMed1992

Isolation and characterization of a sheep cysteine-rich cuticle keratin pseudogene.

The cysteine-rich keratin proteins of the hair cuticle are derived from a multigene family that has been highly conserved during mammalian evolution. We have recently characterized one cuticle keratin gene isolated from a sheep lambda library, and Southern blot analysis of that clone suggested the presence of a second related gene. In the present paper sequencing of the second gene has now indicated that it is a pseudogene, a finding supported by a lack of expression in vivo. The pseudogene appears to have arisen by gene duplication, possibly from the adjacent functional gene. Key mutations seem to have occurred in the promoter and processing signals of this gene to render it non-functional and two in-frame termination codons are present in the coding region. A possible recombination point between sequences encoding glycine-rich repeats was identified that could have lead to the creation of the in-frame termination codons.

Amino Acid Sequence↗
PubMed1991

Regulation of keratin gene expression in hair follicle differentiation.

In hair growth, as the follicle bulb cells rapidly differentiate into either cortical or cuticle hair keratinocytes, about 50-100 keratin genes are transcriptionally activated. However, this complexity can be reduced to several, highly conserved gene families. In studying the regulation of keratin gene expression in the hair follicle we have isolated genes from most of these families and have examined their expression patterns by in situ hybridization. In the cortical keratinocytes striking patterns of keratin gene expression exist, suggesting that different transcriptional hierarchies operate in the various cell types. Comparisons of the keratin gene promoter regions indicates conserved sequence motifs that could be involved in determining these cell specificities. Similarly, we have isolated related sheep and human cuticle keratin genes and find conserved DNA motifs and expression patterns in cuticle cell differentiation. Additionally, the expression of sheep wool follicle IF and high-sulfur keratin genes in transgenic mice suggests that the regulatory DNA elements and proteins of hair keratin genes are functionally conserved between mammals.

Animals↗
PubMed1991

An ultrahigh-sulphur keratin gene of the human hair cuticle is located at 11q13 and cross-hybridizes with sequences at 11p15.

A human hair cuticle ultrahigh-sulphur keratin Q (UHSK) gene (KRN1) has been mapped by Southern analysis of a somatic cell hybrid panel and by in situ hybridization. A probe containing the coding region of this gene mapped to 11pter- greater than 11q21 using the hybrid cell panel and on in situ hybridization mapped to two regions on chromosome 11: the distal part of 11p15, most likely 11p15.5, and the distal part of 11q13, most likely 11q13.5. A probe from the 3' noncoding region of KRN1 mapped to 11q13.5 indicating that this was the map location of the cloned gene. The sequence of 11p15.5 is termed KRN1-like (KRN1L). The results reveal that the cuticle UHSK gene family is clustered in the human genome.

Blotting, Southern↗
PubMed1990

Cyclic hair-loss and regrowth in transgenic mice overexpressing an intermediate filament gene.

We have produced transgenic mice containing up to 250 copies of a sheep wool intermediate filament keratin gene to study the effect of its expression on hair structure and development. Several transgenic lines expressed the gene and in the one containing 250 transgenes, a pattern of hair-loss and regrowth was stably established. Successive waves of hair growth follow periods of denuding like the natural progression of hairs in the mouse hair cycle. By in situ hybridization we have shown that the sheep transgenes are expressed at the correct stage in mouse hair development and at a high level. The transgenic hairs contain not only an elevated level of intermediate filament keratin protein but also a decreased level of the filament-associated proteins. This imbalance disrupts the normal ordered array of these proteins in the cells of the hair cortex and leads to weakened fibres which are prematurely lost.

Amino Acids↗
PubMed1990

Structure and expression of genes for a class of cysteine-rich proteins of the cuticle layers of differentiating wool and hair follicles.

The major histological components of the hair follicle are the hair cortex and cuticle. The hair cuticle cells encase and protect the cortex and undergo a different developmental program to that of the cortex. We report the molecular characterization of a set of evolutionarily conserved hair genes which are transcribed in the hair cuticle late in follicle development. Two genes were isolated and characterized, one expressed in the human follicle and one in the sheep follicle. Each gene encodes a small protein of 16 kD, containing greater than 50 cysteine residues, ranging from 31 to 36 mol% cysteine. Their high cysteine content and in vitro expression data identify them as ultra-high-sulfur (UHS) keratin proteins. The predicted proteins are composed almost entirely of cysteine-rich and glycine-rich repeats. Genomic blots reveal that the UHS keratin proteins are encoded by related multigene families in both the human and sheep genomes. Tissue in situ hybridization demonstrates that the expression of both genes is localized to the hair fiber cuticle and occurs at a late stage in fiber morphogenesis.

Amino Acid Sequence↗
PubMed1989

The keratin BIIIB gene family: isolation of cDNA clones and structure of a gene and a related pseudogene.

The nucleotide sequence of cDNA clones encoding the three major BIIIB high-sulfur wool keratin proteins (BIIIB2, 3, and 4) and the structure of a BIIIB4 gene and a BIIIB3 pseudogene are reported. Although Southern blot analysis indicates that the BIIIB genes comprise a multigene family in the sheep genome, they are poorly represented in genomic DNA libraries. The family sequence homology of the coding region extends into the 5' and 3' untranslated regions and the near 5' flanking region of the BIIIB3 and 4 genes. These homologies suggest that the BIIIB3 and 4 genes represent the latest gene duplication event in the evolution of the BIIIB multigene family. Like the genes coding for other wool keratin matrix protein components, the BIIIB genes have the conserved 18-bp sequence immediately 5' to the initiation codon and also appear to lack introns.

Amino Acid Sequence↗
PubMed1986

Clustered arrangement of keratin intermediate filament genes.

We report here that component members of the keratin intermediate filament (IF) type I and type II gene families of sheep are closely linked but apparently the two families are not. Nine genes, accounting for up to half of the keratin IF gene repertoire, were mapped in four cosmid clones and the linkage between the genes ranged from several kilobases to 20 kilobases. In one cosmid, three tandem type I genes had the same transcriptional arrangement and were regularly spaced. In another cosmid, tandem genes encoding type II keratins were identified and, surprisingly, a solitary exon was discovered in the intergene region between the two type II genes. In a normal gene this exon encodes one of the most conserved amino acid regions of IF proteins, the C-terminal end of the alpha-helical core. Homologous C-terminal protein subdomains were encoded by two wool keratin type II genes and we suggest that this arrangement may also exist in the other wool keratin type II genes.

Animals↗
PubMed1983

Mammalian keratin gene families: organisation of genes coding for the B2 high-sulphur proteins of sheep wool.

We have isolated two genomic clones containing three B2 high-sulphur keratin genes from a sheep genomic library constructed in Charon 4A. These genes do not contain intervening sequences. Two genes, encoding the B2A and B2D proteins are closely linked in the genome, being separated by 1.9 kb, and are transcribed in the same direction. Although there is extensive sequence conservation in the 5' non-coding and coding regions, the 3' non-coding regions diverge both in length and sequence. Within the 5' non-coding region adjacent to the initiating AUG there is a highly conserved 18 bp sequence which is also present in another gene coding for a member of a different, unrelated high-sulphur keratin family. In the B2A-B2D intergene region, tightly linked to the B2D gene, there is a putative, divergently transcribed gene.

Amino Acid Sequence↗
PubMed1982

Organisation of feather keratin genes in the chick genome.

A genomic clone containing sequences of five feather keratin genes has been isolated using cDNA to chicken embryonic feather keratin mRNA as a probe. The clone probably represents part of a longer cluster of tandemly spaced genes; the genes are evenly spaced with a centre to centre separations of 3.3 kb and are transcribed from the same DNA strand, suggesting that the cluster has arisen by a series of tandem duplications. The organisation and complete sequence of the central gene has been determined. The protein encoded by the gene contains 97 amino acids and its sequence is typical of proteins of the embryonic and adult feather family. The transcript from the gene has been deduced to contain a long 3' non-coding region of 435 nucleotides and a 58 base 5' non-coding region interrupted in the gene 21 bases prior to the initiation codon by the gene's only intron of 324 bases.

Amino Acid Sequence↗