365
“Lamprin genes from sea lamprey ( Petromyzon marinus ) contain either seven or
eight exons, with exon 4 being alternatively spliced in all genes, resulting in a total
of six different lamprin transcripts. All exon junctions are of class 1,1. An unusual
feature of the lamprin gene structure is the distribution of the 3′ untranslated region
sequence among multiple exons. Sequence and gene structure comparisons
between lamprins, elastins, and insect structural proteins suggest that the regions
of sequence similarity are the result of a process of convergent evolution,” (Robson
et al. 2000 ).
Here, the results of detailed investigations on elastin distribution in different cartilages of sea lamprey obtained by Wright and co-workers in 1988 using immunohistochemical and ultrastructural methods:
– “Chondrocytes are similar to those in hyaline cartilage.
– Lamprin fi brils and matrix granules, but no collagen fi brils, are found in a matrix
arranged into pericellular, territorial, and interterritorial zones.
– Branchial, pericardial, and nasal cartilages differ from trabecular, annular, and
piston cartilages in the organization of their matrix; as well as in the structural
components of their matrix and perichondria.
– Immunoreactive elastin-like material is present within the perichondria and
peripheral matrices of nasal, branchial, and pericardial cartilages in both larval
and adult lampreys.
– Oxytalan, elaunin, and elastic-like fi bers are dispersed between collagen fi bers in
the perichondrium. The matrix contains lamprin fi brils, matrix granules, and a
band of amorphous material, which is reminiscent of elastin, in the periphery
bordering the perichondrium.
– The presence of elastic-like fi bers and elastin-like material within some lamprey
cartilages implies that this protein may have evolved earlier in vertebrate history
than has been previously suggested,” (Wright et al. 1988 ).
Lysyl pyridinoline was found in high concentration in the elastin-like protein of
lamprey branchial cartilage at a ratio of 7:1 to hydroxylysyl pyridinoline, the form
that dominates in vertebrate collagens (Fernandes and Eyre 1999 ). Both forms of
pyridinoline cross-link were absent from annular cartilage. Desmosine cross-links,
which are characteristic of vertebrate elastin, were not detected in either form of
lamprey cartilage. Pyridinoline cross-links are considered to be characteristic of
collagen, so their presence in an elastin-like protein in a primitive cartilage poses
evolutionary questions about the tissue, the protein, and the cross-linking mechanism. In contrast to ventral aorta in higher vertebrates, the wall of the same organ in
lamprey is composed principally of microfi brils, and not of collagen and elastin.
DeMont and Wright ( 1993 ) “measured the mechanical properties of the ventral
aorta wall of the lamprey, and showed that the architecture provides a mechanical
structure that does produce functional mechanical properties similar to aortae in
higher vertebrates,” (DeMont and Wright 1993 ).
It is proposed “that lampreys possess an ancestral type of cartilage that is similar
to amphioxus gill cartilage. In this respect, gnathostome cartilage can be regarded
as derived from the loss of an elastin-like protein as a cartilage component,”
10.1 Elastin-Like Proteins in Lamprey
“Lamprin genes from sea lamprey ( Petromyzon marinus ) contain either seven or
eight exons, with exon 4 being alternatively spliced in all genes, resulting in a total
of six different lamprin transcripts. All exon junctions are of class 1,1. An unusual
feature of the lamprin gene structure is the distribution of the 3′ untranslated region
sequence among multiple exons. Sequence and gene structure comparisons
between lamprins, elastins, and insect structural proteins suggest that the regions
of sequence similarity are the result of a process of convergent evolution,” (Robson
et al. 2000 ).
Here, the results of detailed investigations on elastin distribution in different cartilages of sea lamprey obtained by Wright and co-workers in 1988 using immunohistochemical and ultrastructural methods:
– “Chondrocytes are similar to those in hyaline cartilage.
– Lamprin fi brils and matrix granules, but no collagen fi brils, are found in a matrix
arranged into pericellular, territorial, and interterritorial zones.
– Branchial, pericardial, and nasal cartilages differ from trabecular, annular, and
piston cartilages in the organization of their matrix; as well as in the structural
components of their matrix and perichondria.
– Immunoreactive elastin-like material is present within the perichondria and
peripheral matrices of nasal, branchial, and pericardial cartilages in both larval
and adult lampreys.
– Oxytalan, elaunin, and elastic-like fi bers are dispersed between collagen fi bers in
the perichondrium. The matrix contains lamprin fi brils, matrix granules, and a
band of amorphous material, which is reminiscent of elastin, in the periphery
bordering the perichondrium.
– The presence of elastic-like fi bers and elastin-like material within some lamprey
cartilages implies that this protein may have evolved earlier in vertebrate history
than has been previously suggested,” (Wright et al. 1988 ).
Lysyl pyridinoline was found in high concentration in the elastin-like protein of
lamprey branchial cartilage at a ratio of 7:1 to hydroxylysyl pyridinoline, the form
that dominates in vertebrate collagens (Fernandes and Eyre 1999 ). Both forms of
pyridinoline cross-link were absent from annular cartilage. Desmosine cross-links,
which are characteristic of vertebrate elastin, were not detected in either form of
lamprey cartilage. Pyridinoline cross-links are considered to be characteristic of
collagen, so their presence in an elastin-like protein in a primitive cartilage poses
evolutionary questions about the tissue, the protein, and the cross-linking mechanism. In contrast to ventral aorta in higher vertebrates, the wall of the same organ in
lamprey is composed principally of microfi brils, and not of collagen and elastin.
DeMont and Wright ( 1993 ) “measured the mechanical properties of the ventral
aorta wall of the lamprey, and showed that the architecture provides a mechanical
structure that does produce functional mechanical properties similar to aortae in
higher vertebrates,” (DeMont and Wright 1993 ).
It is proposed “that lampreys possess an ancestral type of cartilage that is similar
to amphioxus gill cartilage. In this respect, gnathostome cartilage can be regarded
as derived from the loss of an elastin-like protein as a cartilage component,”
10.1 Elastin-Like Proteins in Lamprey