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At least 19 recordsLinked to original sources
PubMed1976

Antibody genes and other multigene families.

The multigene family is a unit of chromosomal organization. Its gene members are closely linked, homologous in sequence, and have overlapping functions. Multigene families can be divided into three categories - simple-sequence, multiplicational, and information - by a variety of structural and functional criteria. Multigene families exhibit two novel evolutionary features - coincidental evolution and rapid change in family size - that suggest that they all share one or more evolutionary mechanisms. Natural selection cannot act directly on individual genes in a family because of their identical or overlapping functions; hence selection must operate on the family as a whole or on blocks of genes within the family. The mechanism(s) for coincidental evolution expand out variant genes within a family so they can be acted on by natural selection, and accordingly, permit multigene families to evolve adaptively. The close linkage of the genes in a family appears to be a consequence of the fact that their ocntrol and evolutionary mechanisms may only operate on tandemly linked genes. New multigene families may evolve from a single gene or from other multigene families. In addition to evolving new functions, the latter mode of evolution generate a new multigene family whose members are preadapted to interact with those of the old family. These family interactions can lead to the evolution of more sophisticated molecular machines or to the regulation of one family by the second. Multigene families may be large or small. The three categories of multigene families allow potential multigene families to be identified and they suggest specific experimental approaches for the study of new families. Some of the most interesting genetic systems under investigation today are known or potential informational multigene families. This is not fortuitous in that many of the most interesting aspects of phenotype are complex ones with correspondingly complex genetic, evolutionary, and regulatory requirements. One of the frontiers in modern genetics is the identification characterization, and understanding of informational multigene families.

Alleles↗
PubMed1975

The organization, expression, and evolution of antibody genes and other multigene families.

The multigene family is a unit of chromosomal organization. Its gene members are closely linked, homologous in sequence, and have overlapping functions. Multigene families can be divided into three catagories: simple-sequence, multiplicational, and informational-by a variety of structural and functional criteria. Multigene families exhibit two novel evolutionary features-coincidental evolution and rapid change in family size-that suggest that they all share one or more evolutionary mechanisms. Natural selection cannot act directly upon individual genes in a family because of their identical or overlapping functions; hence selection must operate upon the family as a whole or upon blocks of genes within the family. The mechanism(s) for coincidental evolution expands out variant genes within a family so they can be acted upon by natural selection and, accordingly, permits multigene families to evolve adaptively. The control mechanisms in multiplicational families appear to promote the rapid expression of many gene copies. In contrast, the regulatory mechanisms of informational families promote the selection, expression, and amplification of appropriate units of information. The close linkage of the genes in a family appears to be a consequence of the fact that their control and evolutionary mechanisms may only operate on tandemly linked genes. New multigene families may evolve from a single gene or from other multigene families. In addition to evolving new functions, the latter mode of evolution generates a new multigene family whose members are preadapted to interact with those of the old family. These family interactions can lead to the evolution of more sophisticated molecular machines or to the regulation of one family by a second. Multigene families may be large or small. The three catagories of multigene families allow potential multigene families to be identified, and they suggest specific experimental approaches for the study of new families. Some of the most interesting genetic systems under the investigation today are known or potential informational multigene families. This is not fortuitous in that many of the most interesting aspects of phenotype are complex ones with correspondingly complex genetic, evolutionary, and regulatory requirements. One of the frontiers in modern genetics is the identification, characterization, and understanding of informational multigene families.

Alleles↗
PubMed1977

Mathematical models for the evolution of multigene families by unequal crossing over.

Mathematical models of homologous but unequal crossing over between sister chromatids are presented. For mispairing by one repeat, the evolution of a multigene family by unequal crossing over can be represented by a linear birth-death process. The fixation rate of one repeat in a multigene family is estimated. For mispairing by more than one repeat, some approximate results are obtained.

Alleles↗
PubMed1978

Organization of the chorion genes of Bombyx mori, a multigene family. I. Evidence for linkage to chromosome 2.

The chorion genes of silkmoths comprise a multigene family that codes for 50 or more highly specialized structural proteins found in the eggshell. A detailed study of the chromosomal organization of these genes was initiated, using inbred stocks of Bombyx mori as a source of electrophoretic variants for genetic markers. Chorion protein patterns were screened on thin-slab polyacrylamide isoelectric focusing gels. A wide range of polymorphism was observed between stocks. However, isoelectric focusing patterns obtained within a stock were nearly homogeneous, indicating that inbreeding has produced a high degree of homozygosis. Testcrosses were carried out to examine the linkage relationships between electrophoretic markers in four inbred stocks. One race (C108) was selected as a standard against which to compare the inheritance of the variants found in the other three stocks. Chorion markers behaved like codominant Mendelian traits in F, crosses. A total of 15 out of 16 C108 markers cosegregated in subsequent testcrosses, indicating that they are linked. These genes were mapped to the second chromosome, using markers Gr and Y.

Animals↗
PubMed1979

Multigene families, histocompatibility systems, transformation, meiosis, stem cells, and DNA repair.

Aging is probably not directly traceable to changes along the whole genome, but to a small portion thereof. The main histocompatibility complex appears to be one among the postulated sets of multigene families responsible. The immortality of transformed cells, the germ line, and possibly certain pluripotential stem cells may suggest common qualitative and/or quantitative differences in DNA repair mechanisms between these cell populations and committed, normal cell populations. A relationship between HLA and at least two diseases showing defective DNA-repair suggests that the same chromosome carrying the main histocompatibility complex may control some repair processes. The correspondence of variation in lifespans in different mouse strains with the DNA repair capabilities and degrees of autoimmune susceptibility of the same strains lends further support to the idea that DNA repair, immune dysfunction and aging in higher animals may be intimately related.

Aging↗
PubMed1979

Evolution of two major chorion multigene families as inferred from cloned cDNA and protein sequences.

Complete or partial sequences are reported from six chorion cDNA clones of the silkmoth Antheraea polyphemus. The proteins encoded belong to the two major chorion protein classes, A and B, each of which is encoded by a multigene family. The sequence comparisons define some major features of the families and suggest how these genes may be evolving. Deletions and insertions might be involved in expanding or contracting internally repetitive regions. Sequence divergence is localized, thus defining sequence domains of distinct evolutionary properties and presumably distinct functions.

Amino Acid Sequence↗
PubMed1979

Population genetics of multigene family with special reference to decrease of genetic correlation with distance between gene members on a chromosome.

A mathematical method is developed which enables us to treat exactly the process of coincidental evolution under mutation, unequal intrachromosomal crossing-over as well as ordinary crossing-over between homologous chromosomes in a finite population of the effective size N. It makes use of finite difference equations involving two quantities denoted by fi and phi i, in which fi is the identity coefficient of two gene members that are i steps apart on the same chromosome and phi i is that of two members i steps apart on two homologous chromosomes. When the number of genes (n) per family is large, the finite difference equations can be approximately by ordinary second-order differential equations which can then be solved analytically. Results obtained by the present method are compared with the corresponding results previously obtained by one of us (T.O.) using conventional diffusion models of gene frequency changes in population genetics. It is shown that the previous results obtained by T.O. regarding second-order statistics are essentially valid, and they give good approximations particularly when N beta is small, where beta is the rate of ordinary interchromosomal crossing-over within the multigene family.

Base Sequence↗
PubMed1978

Silkmoth chorion proteins: sequence analysis of the products of a multigene family.

Five polypeptide components have been isolated from the eggshell (chorions) of a silkmoth. Two are homogeneous on sodium dodecyl sulfate and isoelectric focusing gels, and three contain predominantly two proteins each. Amino acid analyses show that all five components are similar to each other. These proteins have been sequenced from the amino terminus. Homogeneous components yielded single sequences; heterogeneous components yielded two residues at some positions, consistent with their containing two major electrophoretic components. Striking similarities are apparent among all these sequences. These similarities can be increased dramatically by separating each of the three protein mixtures into two sequences and introducing a small number of gaps or insertions. This is due in part to bringing into register a portion that contains short repeating subunits found in all sequences. All proteins are also characterized by a region of high cysteine content near the amino terminus followed by a longer low-cysteine region. The data suggest that these proteins share a common evolutionary origin and are encoded by a multigene family.

Amino Acid Sequence↗
PubMed1979

Use of a cDNA library for studies on evolution and developmental expression of the chorion multigene families.

A cDNA library has been constructed from an RNA preparation highly enriched in silkmoth chorion mRNAs. Many distinct clones have been identified from this library using a stepwise procedure: scoring for infrequent hexanucleotide restriction enzyme recognition sequences; detailed characterization with restriction enzymes that recognize relatively frequent tetranucleotide sequences; probing the arrangement of the corresponding sequences in chromosomal DNA by the Southern procedure; and detailed cross-hybridization analysis. Unique clones, as well as two classes of distinct but related clones, were revealed by hybridization. The cross-hybridization analysis was greatly facilitated by a newly developed, semiquantitative dot hybridization procedure. The same procedure made it feasible to conveniently estimate the relative abundance of several different sequences in an mRNA mixture. Cloned sequences which scored as relatively abundant in total chorion mRNA were tested with stage-specific chorion mRNA at a very stringent criterion of hybridization. They were thus characterized as early, middle or late sequences with respect to development. The characterized cDNA clones can now be used as probes for studying the evolution, chromosomal organization and regulated developmental expression of the chorion multigene families.

Animals↗
PubMed2025

The FIBRILLIN multigene family in tomato, their roles in plastoglobuli structure and metabolism.

Plastoglobuli (PG) are plant lipoprotein compartments, present in plastid organelles. They are involved in the formation and/or storage of lipophilic metabolites. FIBRILLINs (FBNs) are one of the main PG-associated proteins and are particularly abundant in carotenoid-enriched chromoplasts found in ripe fruits and flowers. To address the contribution of different FBNs, independently and in combination, to isoprenoid formation and sequestration, a multiplex gene editing approach was undertaken in tomato. This approach generated a suite of single and high-order fbn mutants that were shown to lack transcripts and respective protein products. The major PG-related FBNs in tomato chosen for this study are SlFBN1, SlFBN2a, SlFBN4 and SlFBN7a. When knocked out independently, functional redundancy was revealed. However, paralog-specific roles were detected regulating specific isoprenoids (e.g. plastochromanol 8) or plastidial esterification capability. In addition, high-order fbn mutants displayed altered isoprenoid chromoplast sequestration patterns, notably with a significant reduction in carotenes (phytoene and phytofluene) in the PG fraction. Proteomic analysis confirmed the absence of PG-core associated proteins, including NAD(P)H-ubiquinone oxidoreductase C1, tocopherol cyclase (VTE1) and phytol esterase (PES1/PYP). Perturbations to the ultrastructure of the plastid were revealed, with aberrant PG formation and morphology predominating in high-order mutants. Global lipidome profiles also highlighted broader changes directly affecting storage and plastid membrane lipids, for example, tri- and diacylglycerides and galactolipid species. Collectively, these results support both structural and metabolic roles of SlFBNs in PGs. The findings expose fundamental aspects of metabolic compartmentalisation in plant cells and the importance of lipoprotein particles for plastid integrity and functionality.

Solanum lycopersicum↗
PubMed2002

A multigene family that interacts with the amino terminus of plasmodium MSP-1 identified using the yeast two-hybrid system.

Merozoite surface protein 1 (MSP-1) is a high-molecular-weight protein expressed on the surface of the malaria merozoite in a noncovalent complex with other protein molecules. MSP-1 undergoes a series of proteolytic processing events, but no precise biological role for the various proteolytic fragments of MSP-1 or for the additional proteins present in the complex is known. Through the use of the yeast two-hybrid system, we have isolated genes encoding proteins that interact with a region of the amino-terminal proteolytic fragment of MSP-1 from the mouse parasite Plasmodium yoelii. This analysis has led to the isolation of two sequence-related molecules, one of which is the P. yoelii homologue of MSP-7 originally described in Plasmodium falciparum. BLAST analysis of the P. falciparum database has revealed that there are six related protein molecules present in this species encoded near each other on chromosome 13. In P. falciparum, we designated these molecules MSRP-1 to -5. Analysis of the P. yoelii database indicates a similar chromosomal organization for the two genes in the mouse parasite species. The three P. falciparum sequences with the highest degree of homology to the P. yoelii sequences isolated in the two-hybrid screen have been characterized at the molecular level (MSRP-1 to -3). Expression analysis indicated that the mRNAs are expressed at various levels in the different asexual stages. Immunofluorescence studies colocalized the expression of the MSRP molecules and the amino-terminal portion of MSP-1 to the surfaces of trophozoites. In vitro binding experiments confirmed the interaction between MSRP-1, MSRP-2, and the amino-terminal region of P. falciparum MSP-1.

Amino Acid Sequence↗
PubMed2025

PAHG: the database of human multi-gene families.

BACKGROUND: In the early vertebrate history, gene duplications, including single-gene, segmental-gene (SSD), and whole-genome duplication (WGD), formed multigene families. Despite efforts to classify metazoan multigene families hierarchically for evolutionary insight, a gap exists in accessible, curated resources for human/vertebrate multigene families. RESULTS: Addressing this, we present the Phylogenomic Analysis of Human Genome (PAHG) database. It focuses on curated multigene families in the human genome, particularly within four paralogons: HOX-bearing (Hsa:2/7/12/17), FGFR-bearing (Hsa:4/5/8/10), MHC-bearing (Hsa:1/6/9/19), and chromosomes 1/2/8/20. CONCLUSION: The current PAHG version details the phylogenetic history of 221 human multigene families (1247 gene members) with 15,231 protein sequences from diverse metazoans. It provides insights into gene duplication timings, co-duplication events, and their relationships with human genome syntenic organization. The PAHG database addresses the lack of accessible resources, offering valuable information on human/vertebrate multigene family evolution. Access the PAHG database at: https://www.pahgncb.com/ and http://pahg.qau.edu.pk/ . This resource enriches our understanding of vertebrate genetic evolution.

Humans↗
PubMed1976

A mathematical approach to the analysis of diversity in antibody gene families.

In this article, we develop a mathematical approach for the analysis of diversity in antibody gene families. This approach is arrived at by examing two general questions about protein populations: (1) What is a relative measure of the diversity exhibited by one protein family when compared with a second? (2) What is the probability that two protein populations were derived from a single common population? These quantitative approaches permit a variety of precise evolutionary, genetic, and developmental questions to be asked of antibody gene families. Using this methodology, we demonstrate that the diversity in mouse K-immunoglobulin chains is considerably greater than in their human K counterparts. We also show that the variable (Vl) regions of light chains associated with IgG and IgA immunoglobulins in the mouse appear to have been derived from a common population of Vl genes. This approach also can be used to analyse sequence data from other informational multigene families.

Amino Acid Sequence↗