Synaptonemal complex analysis in goats carrying the 5/15 Robertsonian translocation

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Synaptonemal complex analysis in goats carrying the

5/15 Robertsonian translocation

Mej Amaral, W Jorge

To cite this version:

Original

article

Synaptonemal complex analysis

in

_goats

_carrying

the

_5/15

Robertsonian

translocation

MEJ

Amaral

W

_Jorge

₂

1

Instituto

de

_{Biociencias, Departamento}

de

_Genetica,

_UNESP,

Campus

de Botucatu, 18618-000, Botucatu, Sdo

Paulo;

2

Instituto de Ciencias

_{Biológicas, Departamento}

de

_{Biologia Geral,}

Universidad Federal de Minas

_{Gerais, 31,}

270-010 Belo

_Horizonte,

Minas

_Gerais,

Brasil

(Received

24

_February

_1993;

_accepted

21

_February

₁₉₉₄₎

Summary -

Synaptonemal complexes

were

_{analysed by}

electron

_microscopy

in 2 bucks

heterozygous

for the

_5/15

Robertsonian translocation. The cis

_{configuration}

_(free

homo-logous

5 and 15 chromosomes on the same side of the

5/15

translocated

chromosome)

was

found in all 50 cells examined. This feature is considered a

_prerequisite

for the

development

of balanced _gametes. No association between the sex bivalent and trivalent was observed.

meiosis

/ synaptonemal

complex

/

trivalent

_/

Robertsonian translocation

_/

goat

Résumé - _L’analyse du _{complexe synaptonémique} de 2 boucs porteurs de la translo-cation robertsonienne

_{5/15. L’analyse}

du

_{complexe synaptonémique}

a été

_effectuée,

en

microscopie

électronique,

chez 2 boucs

_{hétérozygotes}

pour la translocation robertsonienne

5/15.

La

_{configuration}

cis

_(chromosomes

_homologues

5 et 15 situés du même côté du

chromosome-transloqué

5/15)

a été trouvée dans les 50 cellules examinées. Cette

carac-téristique

est considérée comme une condition

_préalable

au

_{développement}

de

_gamètes

équilibrés.

Aucune association entre le bivalent sexuel et le trivalent n’a été détectée.

méiose

_/

_complexe synaptonémique

/

trivalent

_/

translocation robertsonienne

_/

chèvre

*

Correspondence

and

_reprints:

1109 Southwest

_{Parkway, Apt 1702, College Station,}

INTRODUCTION

Electron

_microscopic

_(em)

_analysis

of

_{synaptonemal complexes}

_(SC)

in the meiotic

cells of domestic animals

_carrying

chromosomal aberrations

_began

with the works of Switonski et al

₍₁₉₈₇₎

and Gabriel-Robez et al

_(1986).

Karyotype analysis

of 2 Saanen male

_goats

with 2n = 59 chromosomes indicated

the _presence of a submetacentric chromosome. The

_G-banding

_technique

was used

to

_identify

the marker chromosome as a fusion of chromosomes 5 and 15. Little research has been documented

_concerning

SC in

_goats

_possessing

either normal or translocated chromosomes. To

_investigate

the effect of the

_5/15

translocation on the

reproductive

capacity

of the

_heterozygous

animals,

SC formation and the behaviour of the trivalent

_5/15;

_{5 ;15}

was studied at the

_pachytene

_stage

of meiosis.

MATERIALS AND METHODS

Two Saanen male

goats

(Capra hircus),

both

_59,

XY,

t(5 ;15)

heterozygous

for the

translocation were studied. Hemi-castration was

_immediately

followed

_by

testicular dissection with a

scalpel,

in Hank’s medium.

The

_preparations

of

_{microspread samples}

were made

_according

to the

_technique

presented

by

Solari

_(1980).

A

_droplet

of the testicular cell

_suspension

was added

to

_{approximately}

5 ml of a

0.5%

NaCI

_hypotonic

solution. The

_spread

nuclei were then

_{picked up by touching}

slides

_pre-coated

with

_plastic

film on the surface of the solution. The slides were

_immediately

immersed in a

Coplin jar containing

SDS fixative

_(4%

_{paraformaldehyde}

and

0.03%

_{SDS, pH}

8,

adjusted

with sodium tetraborate

_buffer)

and incubated for 5 min at room

_temperature.

The slides were then held on the surface of

0.4%

_{Photoflo, pH}

8 for 30 s and allowed to

_air-dry.

Silver nitrate

_staining

was

_performed

as described

_by

Howell and Black

_(1980).

Nuclei were selected

by light

_microscopy

and covered with

50/75

mesh

_grids.

The

plastic film,

with the attached nuclei and

_grids,

was detached from the slide

_by

floating

on water and collected with resined paper. Under em, the

magnification

was 1 600 x.

_Micrographs

were

_enlarged

5 x. The SC

_lengths

(mm)

were measured

individually.

Intact nuclei

containing

a

complete

SC set were used to construct

karyotypes.

The normal autosomal bivalents were

_{arranged by decreasing}

size and

aligned by

the kinetochore. Each trivalent

_5/15,

5 and 15 was

_put

in the

_position

of bivalent 5

_(see

_fig

2

_below).

The XY bivalent

_occupied

the last

_position.

The trivalent

_5/15,

5 and 15 was

_{photographed individually}

and

_enlarged

4200 x for

RESULTS

Twenty-seven

autosomal

bivalents,

one autosomal trivalent and the sex bivalent

(figs

1 and

₂₎

were observed in

_spermatocyte

_preparations

from the

heterozygous

5/15

translocated buck

_(2n

=

59).

In all the

analysed

nuclei

(50),

the free

homologous

chromosomes 5 and 15

paired

in the cis

_{configuration}

_(figs

3 and

4).

In the

_trivalent,

the

_{pericentromeric region}

of the free

_homologous

5 and 15 was not

_paired

at

_{early pachytene}

_{(fig 3).}

At

_{mid-pachytene, heterosynapsis}

was observed between the

_{pericentromeric regions}

of the free

_homologues

5 and 15. At late

_pachytene,

the

_synaptic

_adjustment

was

_complete

and the centromeric

_tips

of the free

_homologues

5 and 15 were

_{completely paired}

with the translocated

corresponding

arms

_{(fig 4).}

The

_{kinetochores, however,}

did not fuse and

_stayed

in

juxtaposition.

The trivalent

_5/15,

5 and 15 was not observed to be associated with the sex bivalent.

DISCUSSION

In this _paper, the trivalent showed the

_{pericentromeric region}

of the free

_homologues

5 and 15 not

_paired

at

_{early pachytene.}

Late

_synapsis

seems to be a characteristic of the trivalents as is described in bovine

(Switonski

et

_al,

_1987),

and Lemur

_hybrids

(Moses

et

_al,

_1979).

In chinese hamster

_bivalents,

the centromeric

_region

is also the last to form SC

_{(Moses, 1977).}

The kinetochore of the free

_homologues

5 and 15

_paired

_{preferentially}

in the cis

configuration

with their

_homologue

_portions

in the

_5/15

translocated chromosome and were visible

_throughout

the

_pachytene.

Moses et al

₍₁₉₇₉₎

observed the same

phenomenon

while

_studying

trivalents in Lemur

hybrids

under em. Data obtained with

Capra

hircus agree with the results of Moses et al

₍₁₉₇₉₎

who

_suggested

that both acrocentric kinetochores maintain the cis

_{configuration}

_{independently}

_during

synapsis.

This excludes the

_probability

of variable

_pairing

faces and leads to the conclusion that a

_single

_pairing

face on the translocated chromosome determines the

_plane

of SC

_assembly.

The cis

_{configuration}

was also found in the

rodent,

Sigmodon falviventer, by

light

microscopy

(Elder

and

_Pathak,

₁₉₈₀₎

and no

_fertility

reduction was observed. When the

_heterozygous

buck was crossed with normal

homozygous

or

hetero-zygous, females, there was no

_fertility

reduction

_according

to

_Goncalves

_(personal

communication).

These data _may be

_interpreted

as an indirect

_sign

of a non-random

segregation

of the trivalent chromosomes. Moses et al

₍₁₉₇₉₎

noted that the normal

fertility

rate observed in Lemur

_hybrids

in related to a mechanism which increases the

_frequency

of balanced

_gametes.

In

_addition,

such a mechanism would

specify

the

_symmetric

_arrangement

of free

_homologues

of the trivalent at

_pachytene.

The

_hypothesis

which

suggests

that the

symmetry

presented by

the translocated chromosomal arms _may influence the

_{configuration,}

either cis or

_trans,

should be considered. It may be well

accepted

that the more

_asymmetric

the translocation

arms, as in bovine translocation

1/29,

the

_greater

the

_probability

of

_observing

the

trans

_{configuration.}

Previous studies which

present

trivalents in the cis

rats with

_t(10;11)

_(Elder

and

Pathak,

1980)

and humans with

_{t(13;14) (Luciani}

et

_al,

₁₉₈₄₎

_present

_very

_symmetric

translocated chromosomal arms.

_Perhaps

the

trans

_{configuration}

becomes less

probable

as observed if the chromosomal arm ratio

(long arm/short arm)

approaches

1.00.

There are

morphological

differences _among the trivalents that result from centric fusion in

_{bovines, humans,}

rodents and

_caprines,

and

_they

_may influence the association with the sex bivalent. The variation in the

_position

of the acrocentric chromosomes

_neighbouring

the sex vesicle

_produces

free

_parts

with a

_stronger

tendency

to

_pair

with the sex chromosomes. This variable

_tendency

could

explain

the variation which occurs in the

_{phenotypic expression}

of

fertility

in men with centric fusion

_(Johannisson

et

_al,

_1987).

Bouvet et al

₍₁₉₈₉₎

_suggest

that the absence of association

between

the sex bivalent and the autosomal trivalent could

explain

the normal

_{spermatogenesis}

_{presented by}

cattle

_carrying

chromosomal

_{translocations,}

while mice and humans

_carrying

similar translocations are infertile due to the

presence of such associations.

In the

present

case, the trivalent was not observed in association with the sex bivalent. In studies on humans

(Johannisson

et

al,

1987)

and mice

_(Forejt

et

al,

1981)

it was assumed that the

_reciprocal

and Robertsonian translocations may

bring

about either

_sterility

or

infertility

if the

unpaired

_autosomes,

or autosomal

segments,

pair

with the X chrosomome. The authors have

_suggested

that the

proximity

of the autosomal

_segment

with the X chromosome may interfere with its

inactivation _process

_{by harming}

the

_germinative

cell. This kind of association has often been found in infertile men with balanced Robertsonian translocation between

chromosomes 13 and 14

_(Luciani

et

_al,

₁₉₈₄₎

and 14 and 21

_(Rosenmann

et

_al,

_1985).

In all of the

_micrographs

_observed,

the

_phase

of

_unpairing

in the

_{pericentromeric}

region

of the acrocentric 5 and 15 was restricted to the

_beginning

of

_pachytene

when the Y chromosome had also started

_pairing

with the X chromosome.

ACKNOWLEDGMENTS

We would like to thank A

Solari, University

of Buenos

_Aires,

for

_help

in the

_technique

adaptation,

Y

_{Yonenaga-Yassuda,}

Bioscience

_Institute,

USP,

Sao

_Paulo,

for assistance in

the

_analysis

of the

_results,

EA

_Greg6rio

and MH Moreno, Electron

_{Microscopy Center,}

IB, UNESP, Botucatu,

for utilization of the electron

_microscope

and CAPES for support

of the

_project.

REFERENCES

Bouvet

_A,

Popescu CP,

Giovanni-Macchi

_AM,

Colombo

G,

Molteni L

₍₁₉₈₉₎

Synaptonemal complex analysis

in a bull

_carrying

a

_{4 ;8}

Robertsonian translocation.

Ann Genet

_32,

193-199

Elder

_FFB,

Pathak S

₍₁₉₈₀₎

_Light

_microscopic

observations on the behavior of silver-stained trivalents in

_pachytene

cells of

_{Sigmodon fulviventer}

_(Rodentia,

Muridae)

heterozygous

of centric fusion.

_Cytogenet

Cell Genet

_27,

31-38

Forejt J,

Gregorov S,

Goetz P

₍₁₉₈₁₎

XY

_pair

associates with the

_synaptonemal

Gabriel-Robez

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Y

(1986)

Meiotic association between the XY chromosomes and the autosomal

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_{46, XY,}

T(19;22)

and

_{46, XY,}

t(17;21).

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Cell

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_WM,

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impairment

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Cell Genet

45,

222-230

Luciani

_JM,

Guichaoua

_MR,

Mattei

_A,

Morazzani MR

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_{Pachytene analysis}

of a man with a

_13q;14q

translocation and

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Cell Genet

38,

14-22

Moses MJ

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_Synaptonemal

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karyotyping

in

_{spermatocytes}

of the

Chinese hamster

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of the autosomal

_complement

in

_{spread preparations.}

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_PA,

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₍₁₉₇₉₎

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heteromorphic

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A,

Wahrman

J,

Richler

C,

Voss

R,

Persitz

A,

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Gustavsson

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