Synaptonemal complex behaviour in a bull homozygous for the 1;29 Robertsonian translocation

(1)

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Synaptonemal complex behaviour in a bull homozygous

for the 1;29 Robertsonian translocation

A Bouvet, Ep Cribiu

To cite this version:

(2)

Short

note

Synaptonemal complex

behaviour

in

a

bull

homozygous

for the

_1;29

Robertsonian

translocation

A Bouvet EP Cribiu

INRA,

Centre de Recherche de

_Jouy

Laboratoire de

_{Cytogénétique,}

78350

_{Jouy-en-Josas,}

France

(Received

24

_{April 1990; accepted}

13 June

₁₉₉₀₎

Summary -

Analysis

of

_synaptonemal

_complexes

from a bull

_homozygous

carrier for the

1;29

Robertsonian translocation showed the presence of 28 autosomal bivalent

figures

including

one with

_{subtelocentrically}

located kinetochores. No association with the sex

vesicle was detected. In the X — Y

_bivalent,

a

_pairing

_segment

existed between the

extremity

of the X and Y chromosomes

_throughout

pachytene.

A gap

separating

that

complex

from the rest of the Y chromosome was _apparent,

regardless

of the stain used. The

results of this

study

confirm that there is no meiotic

impairment

when this

_homozygous

translocation is _present.

cattle

/ meiosis

/ synaptonemal complexes

/ Robertsonian

translocation

Résumé - Comportement des complexes synaptonématiques chez un taureau

ho-mozygote pour la translocation robertsonienne 1;29. L’examen de

_complexes

synap-tonématiques

d’un taureau

_homozygote

pour la translocation robertsonienne

1;29

a révélé la

_présence

de 28 bivalents

_autosomiques

dont 1 montrant des kinétochores en

_position

subterminale. Aucune association avec la vésicule sexuelle n’a été notée. Les extrémités des chromosomes X et Y sont restées

_appariées

durant tout le stade

_pachytène.

La

sépara-tion entre ce

_complexe

et l’extrémité distale du chromosome Y a été

_{régulièrement notée,}

quel

que soit le colorant

employé.

Les résultats de cette étude

_confirment

que la

présence

de

cette translocation robertsonienne à l’état

_homozygote

n’a pas

d’e,$’et négatif sur

la méiose. bovin

_/

complexe synaptonématique

/

méiose

_/

translocation robertsonienne

INTRODUCTION

The

_analysis

of

_synaptonemal

_complexes

behaviour in

_pachytene

cells has now been

incorporated

into the arsenal of methods used to

_investigate

the

_impact

on

fertility

of chromosome translocations in male carriers. In

humans,

the

_negative

_impact

of

certain Robertsonian translocations on male

_fertility

has been attributed to the association between the

_rearranged

chromosomes and the sex

vesicle

_(Luciani

et

_al,

1984;

Rosenmann et

_al,

_1985).

In

_cattle,

_synaptonemal

_complexes

have also been

examined in

_heterozygous

carriers for

_1;29

_(Switonski

et

_al,

_1987),

_4;8

_(Bouvet

et

*

(3)

al,

1989)

and both

_1;29

and

_9;23

Robertsonian translocations

_(Bouvet

and

_Cribiu,

1990)

but no association with the sex vesicle could be noted. The

present

study

reports

the

_analysis

of

_synaptonemal

_complex

behaviour in

_{spermatocytes}

from a

bull

_homozygous

carrier for the

_1;29

Robertsonian translocation.

MATERIALS AND METHODS

The

1;29 Robertsonian translocation

carrier examined in this

_study

was a Blonde

d’Aquitaine

bull. After hemicastration of the

_bull,

the removed testis was immersed into a container filled with HAM’s F-12 culture

_medium,

and was

_processed

immediately

for electron

_microscopy.

The testis was cut _openwith a

scalpel

blade and a small

_piece

of tissue was removed.

_Droplets

of

_hypotonic

0.2

_mol/1

Sucrose solution were

_dispersed

on the surface of

_grease-free

_microscopic

slides

_precoated

with

0.5%

Optilux

in

_chloroform,

and the tissue

_sample

was

_lightly

_pressed

in one

swift touch on

_top

of each

_droplet,

to

_spread

the

_{spermatocytes.}

The slides were

dried and fixed with

4%

_{paraformaldehyde}

in 0.1

_mol/1

sucrose. After

fixation,

cells

were stained with either a solution of 1

_{part 4%}

_{phosphotungstic}

acid

_(PTA)

_plus

3

_{parts 95%}

ethanol or with

50%

silver nitrate. After

_floating

off the

plastic

film

on

_water,

100-mesh _copper

_grids

were used to

_pick

_upselected areas.

_Micrographs

were taken at a

_{magnification}

of

_{3 000 x,}

_using

a

_Philips

CM12 transmission electron

microscope

at 120 kV.

In cells

_showing

well-defined

_complexes,

the arm ratio

_{(long arm/short arm)}

was

calculated for the bivalent

_{figure showing}

subtelocentric kinetochores. The

_negatives

were

_placed

on a Biocom

_{photometric viewing table,}

and the

_image

was transmitted

by

a video camera

(Canon

macro

50x3.5)

to a Barc monitor linked to a

_Compaq

386

microcomputer.

All measurements were made on the screen

_using

MIMAL

_image

analyser

software.

RESULTS AND DISCUSSION

In 17

_{surface-spread}

_{spermatocytes}

of the

_1;29

_homozygous

translocation carrier

bull,

29 bivalents could be

_{distinguished.}

The 28 autosomal bivalents showed the normal structure of 2 lateral

_elements,

one central

_element,

_densely

stained kineto-chores and well-defined attachment

_plaques.

The X - Y bivalent was

easily

identi-fiable

_by

its darker

_{staining intensity.}

The 28 autosomal bivalents could be classified

in

_{decreasing length,}

the

_largest

bivalent

_figure

_showing

a

_pair

of

_well-aligned

sub-telocentric

_{kinetochores,}

whereas the others showed terminal kinetochores

_{(fig 1).}

By

the end

_{of pachytene,}

all autosomal

complexes

showed

_{complete synapsis.}

In the 17 cells

_examined,

the average arm ratio for the

_1;29

bivalent was 3.06 ! 0.86. This agrees

only partially

with the

corresponding

index of 3.01-3.38 of the mitotic

_1;29

translocation chromosome

_(Gustavsson,

_1969;

_Popescu,

_1971).

The

_1;29

bivalent

figure

remained

independant

from the sex vesicle in all cells examined. The X — Y

bivalent showed a

_pairing

_segment

at the

_extremity

of the X chromosome

throu-ghout pachytene

and an unstained _gapbetween that

_segment

and the terminal

_part

of the Y chromosome was

_generally

noted

_{(fig 2).}

All these features were noted in

(4)

Complete

pairing

of autosomal axes

by

the end of

pachytene,

absence of asso-ciation with the sex vesicle and the presence of an XY

pairing

segment

at one

extremity

of the X chromosome

_throughout

_pachytene,

were similar to the features

already

noted in normal and

_heterozygous

bulls

_(Switonski

and

_Gustavsson,

_1986;

Switonski et

_al,

_1987;

Bouvet et

al, 1989;

Dollin et

al, 1989;

Bouvet and

Cribiu,

1990).

The

_separation

between the X —Y

_{synaptonemal complex}

and the distal

_part

of the Y chromosome had

_already

been

_reported

in PTA stained material

_(Switonski

and

_Gustavsson,

_1986;

Bouvet et

_al,

_1989).

The results of the

_present

_study

and that of Dollin et al

_(1989),

_using

silver nitrate and PTA

_clearly

showed that it is a constant feature of X — Y

_bivalents,

_regardless

of the stain used. Whether this gap is an unstained

segment

of the Y

_chromosome,

due to a different molecular

organization resulting

in a low

_staining

_ability

(Bouvet

et

_al,

₁₉₈₉₎

or whether it is

the result of the mechanical

separation

of the free end of the Y chromosome from

the X — Y

_{synaptonemal complex}

at the

_extremity

of the X

chromosome,

during

(5)

ACKNOWLEDGMENTS

The authors wish to thank J

_P16chon,

M Rousseau and their

_laboratory

staff

(CRJ-INRA,

78350

_{Jouy-en-Josas)}

for their efficient technical

_help

in various

_aspects

of the electron

_{microscopic procedures.}

_Analysis

of the

_micrographs

would not

have been

_possible

without the collaboration of Dr J Serviere and Mrs G Gendrot

(laboratoire

de

_physiologie

_sensorielle,

_CRJ),

who

_{graciously agreed}

to let us use

their Biocom

_{Image Analyzer}

apparatus.

Thanks are also extended to Mr G Fabre

and his technical staff at the Carmeaux field station for their invaluable

_help

in the

housing

and

_caring

of the animal and their assistance

_during

the

_{surgical procedure.}

REFERENCES

Bouvet

_A,

Cribiu EP

₍₁₉₉₀₎

_Analysis

of

_synaptonemal

_complexes

behaviour in a subfertile bull

_{carrying 1;29}

and

_9;23

Robertsonian translocations.

_Zuchthygiene

(6)

Bouvet

_A,

Popescu

CP,

De Giovanni-Macchi

A,

Colombo

_G,

Molteni L

₍₁₉₈₉₎

Synaptonemal complexes

analysis

in a bull

_carrying

a

_4;8

Robertsonian translo-cation. Ann

_{Genet 32,}

193-199

Dollin

_{A, Murray}

_JD,

Gillies CB

₍₁₉₈₉₎

_{Synaptonemal complex}

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cattle. I

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and the normal full bloods. Genome

_{32, 856-864}

Gustavsson I

₍₁₉₆₉₎

_Cytogenetic,

distribution and

_phenotypic

effects of a

translo-cation in Swedish cattle. Hereditas

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68-169

Luciani

JM,

Guichaoua

_MR,

Mattei

_A,

Morrazzani MR

₍₁₉₈₄₎

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Cytogenet

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Popescu

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₍₁₉₇₁₎

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Switonski

_M,

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₍₁₉₈₇₎

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