1: EXS. 2001;(91):1-10. 

The one-to-four rule and paralogues of sex-determining genes.

Ohno S.

Beckman Research Institute of the City of Hope, 1450 East Duarte Road, Duarte,
California 91010-3000, USA.

Because of two successive rounds of tetraploidization at their inception, the
vertebrates contain four times more protein-coding genes in their genome than
the invertebrates: 60,000 vs. 15,000. Consequently, each invertebrate gene has
been amplified to the maximum of four paralogous genes in vertebrates: the
one-to-four rule. When this rule is applied to genes pertinent to gonadal
development and differentiation, the following emerged: (i) Two closely related
zinc-finger transcription factor genes in invertebrates have been amplified to
two paralogous groups in vertebrates. One consisted of EGR1, EGR2, EGR3 and
EGR4, whereas the only known paralogue of the other is WT1, which controls the
developmental fate of the entire nephric system, and therefore of gonads.
Interestingly, EGR1 and WT1 act as antagonists of each other in nephroblastic
cells. (ii) SF-1, which controls the fate of two steroid hormone-producing
organs, adrenals and gonads, is descended from the invertebrate Ftz-F1 gene, and
its only known paralogue is GCNF-1. (iii) The Y-linked SRY, the mammalian
testis-determining gene, is a paralogue neither of SOX3 (SRX) nor of SOX9. Its
ancient origin suggests that SRY once became extinct in earlier vertebrates,
only to revive itself in the mammalian ancestor. (iv) Inasmuch as four
paralogues of one invertebrate nuclear receptor gene have differentiated to
receptors of androgen, mineralocorticoid, glucocorticoid and progesterone, there
should at most be four paralogous estrogen-receptor genes in the vertebrate
genome. It is likely that one of them plays a pivotal role in the
estrogen-dependent sex-determining mechanism so commonly found among reptiles,
amphibians and fish.

Publication Types:
    Review
    Review, Tutorial

PMID: 11301594 [PubMed - indexed for MEDLINE]


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2: Cell Mol Life Sci. 1999 Jun;55(6-7):824-30. 

The one-to-four rule and paralogues of sex-determining genes.

Ohno S.

Beckman Research Institute of the City of Hope, Duarte, California 91010-3000,
USA.

Because of two successive rounds of tetraploidization at their inception, the
vertebrates contain four times more protein-coding genes in their genome than
the invertebrates: 60,000 versus 15,000. Consequently, each invertebrate gene
has been amplified to the maximum of four paralogous genes in vertebrates: the
one-to-four rule. When this rule is applied to genes pertinent to gonadal
development and differentiation, the following emerged: (i) Two closely related
zinc-finger transcription factor genes in invertebrates have been amplified to
two paralogous groups in vertebrates. One consisted of EGR1, EGR2, EGR3 and
EGR4, whereas the only known paralogue of the other is WT1, which controls the
developmental fate of the entire nephric system, and therefore of gonads.
Interestingly, EGR1 and WT1 act as antagonists of each other in nephroblastic
cells. (ii) SF-1, which controls the fate of two steroid hormone-producing
organs, adrenals and gonads, is descended from the invertebrate Ftz-F1 gene, and
its only known paralogue is GCNF-1. (iii) The Y-linked SRY, the mammalian
testis-determining gene, is a paralogue neither of SOX3 (SRX) nor of SOX9. Its
ancient origin suggests that SRY once became extinct in earlier vertebrates,
only to revive itself in the mammalian ancestor. (iv) Inasmuch as four
paralogues of one invertebrate nuclear receptor gene have differentiated to
receptors of androgen, mineralocoticoid, glucocorticoid and progesterone, there
should at most be four paralogous estrogen-receptor genes in the vertebrate
genome. It is likely that one of them plays a pivotal role in the
estrogen-dependent sex-determining mechanism so commonly found among reptiles,
amphibians and fish.

Publication Types:
    Review
    Review, Tutorial

PMID: 10412365 [PubMed - indexed for MEDLINE]


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