Biomedical subjects

Melanie Wilson

Publications and source records attributed to Melanie Wilson.

23 records · Page 2Linked to original sources

PubMed2002

The IgH locus of the channel catfish, Ictalurus punctatus, contains multiple constant region gene sequences: different genes encode heavy chains of membrane and secreted IgD.

The delta-chain of catfish IgD was initially characterized as a unique chimeric molecule containing a rearranged VDJ spliced to C micro 1, seven C domain-encoding exons (delta1-delta7), and a transmembrane tail. The presence of cDNA forms showing splicing of delta7 to an exon encoding a secretory tail was interpreted to indicate that membrane (deltam) and secreted (deltas) forms were likely expressed from a single gene by alternative RNA processing. Subsequent cloning and sequence analyses have unexpectedly revealed the presence of three delta C region genes, each linked to a micro gene or pseudogene. The first (IGHD1) is located 1.6 kb 3' of the functional C micro (IGHM1). The second (IGHD3) is positioned immediately downstream of a pseudo C micro (IGHM3P), approximately 725 kb 5' of IGHM1. These two delta genes are highly similar in sequence and each contains a tandem duplication of delta2-delta3-delta4. However, IGHD1 has a terminal exon encoding the transmembrane region, whereas IGHD3 has a single terminal exon encoding a secreted tail. The occurrence of IGHD3 immediately downstream of a micro pseudogene indicates that the putative deltas product may not be expressed as a chimeric micro delta molecule. Western blots and protein sequencing data indicate that an IGHD3-encoded protein is expressed in catfish serum. Thus, catfish deltam transcripts appear to originate from IGHD1, whereas deltas transcripts originate from IGHD3 rather than, as previously inferred, from a single expressed delta gene. The third delta (IGHD2) is associated with a pseudo C micro (IGHM2P); its presence is inferred by Southern blot analyses.

Amino Acid Sequence↗

PubMed2002

Immortal and mortal clonal lymphocyte lines from channel catfish: comparison of telomere length, telomerase activity, tumor suppressor and heat shock protein expression.

Channel catfish autonomous (immortal) and nonautonomous (mortal) leukocyte lines were phenotyped with respect to telomere length and the expression of telomerase, Hsp70 and p53, potentially important factors in cellular immortalization. The autonomous cells constitutively expressed telomerase whereas the nonautonomous cells expressed this activity only transiently. This observation, coupled with the low telomerase activity level seen in freshly isolated leukocytes, suggests that telomerase expression in catfish leukocytes is activation induced. In contrast both types of cell lines exhibited quite similar patterns of significantly shortened telomeres, suggesting that telomerase does not stabilize catfish telomeres until a critical short length is reached. Northern analyses indicated that, like telomerase, Hsp70 gene expression was constitutive in autonomous cells and transient in nonautonomous cells. In contrast, p53 mRNA levels appeared similarly low and noncycling in both long-term cultured types of catfish cells, regardless of the culture situation. Furthermore it was noted, by Western analyses, that both types of cells display multiple sized forms of p53 proteins. This latter observation implies that truncation of p53 protein is probably not directly involved in the in vitro immortalization process of channel catfish leukocytes.

Animals↗

PubMed2002

Channel catfish cytotoxic cells: a mini-review.

The use of allogeneic and autologous lymphoid cell lines has facilitated studies of cytotoxic T lymphocytes (CTL) and natural killer (NK)-like cells in channel catfish. Naïve catfish leukocytes were shown to spontaneously kill allogeneic cells and virally-infected autologous cells without the need for prior sensitization, and allogeneic cytotoxic responses were greatly enhanced by in vitro alloantigen stimulation. Both catfish CTL and NK-like cells have been successfully cloned from these alloantigen-stimulated cultures, and represent the first cytotoxic cell lines derived from any ectothermic vertebrate. These cloned cytotoxic cells contain granules and likely induce apoptosis in sensitive targets via a putative perforin/granzyme mechanism. In addition, some catfish CTL clones may also kill targets by an additional mechanism, possibly by Fas/FasL-like interactions. Importantly, these cytotoxic cells do not express the marker for catfish nonspecific cytotoxic cells (NCCs), and thus represent cell types distinct from NCCs. The use of monoclonal antibodies against the catfish F and G immunoglobulin light chain isotypes revealed the presence of a putative Fc receptor for IgM (Fc mu R) on some catfish NK-like cells that appears to 'arm' these cells with surface IgM. In addition, a potentially important monoclonal antibody (CC41) developed against catfish NK-like cells was found to recognize an approximately 150kDa molecule on the surface of catfish cytotoxic cells. These studies clearly demonstrate that catfish possess an array of different cytotoxic cells. The availability of various cloned cytotoxic cell lines should enable unambiguous functional studies to be performed in ways not currently possible with any other fish species.

Animals↗

PubMedDate not supplied

Construction and characterization of a BAC library from a gynogenetic channel catfish Ictalurus punctatus.

A bacterial artificial chromosome (BAC) library was constructed by cloning HindIII-digested high molecular weight DNA from a gynogenetic channel catfish, Ictalurus punctatus, into the vector pBeloBAC11. Approximately 53,500 clones were arrayed in 384-well plates and stored at -80 degrees C (CCBL1), while clones from a smaller insert size fraction were stored at -80 degrees C without arraying (CCBL2). Pulsed-field gel electrophoresis of 100 clones after NotI digestion revealed an average insert size of 165 kb for CCBL1 and 113 kb for CCBL2. Further characterization of CCBL1 demonstrated that 10% of the clones did not contain an insert. CCBL1 provides a 7.2-fold coverage of the channel catfish haploid genome. PCR-based screening demonstrated that 68 out of 74 unique loci were present in the library. This represents a 92% chance to find a unique sequence. These libraries will be useful for physical mapping of the channel catfish genome, and identification of genes controlling major traits in this economically important species.

Animals↗

PubMedDate not supplied

Rickets.

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Calcium, Dietary↗