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The Dag defect of the tail of the bull sperm. Studies on the inheritance and pathogenesis
THERIOGENOLOCY THE DAG DEFECT OF THE TAIL OF THE BULL SPERM. STUDIES ON THE INHERITANCE AND PATHOGENESIS(a) H.H. Koefoed-Johnsen(b), J.B.
Anderset+),
E. Andresencd
E. Blomce) and H. Philipsenlb) (b) Institute for Animal Reproduction, The Royal Veterinary and Agricultural University (c) The Veterinary Services (d) Department of Genetics of Domestic Animals, The Royal Veterinary and Agricultural University (e) The State Veterinary Serum Laboratory, Copenhagen, Denmark Received for Publication: (j/11/80 ABSTRACT During the period 1963-1979, 15 spontaneous cases of the sterilizing Dag defect of the sperm tail in Danish Jersey bulls have been examined. The pedigree of these bulls could be traced back throuqh both paternal and maternal lines to a common ancestor bull born in 1934. The probable heredity of the defect was tested in a sire-daughter breeding experiment. Six bulls out of 38 sons born produced semen typical of the Dag defect thus confirming that the defect is due to the presence of an autosomal recessive factor. Systematic examination of the epididymal contents from 17 bulls revealed that the defect consistently developed in the distal part of the epididymal caput. Neither biophysical and biochemical qualities of the epididymal contents nor the histological appearance of the duct epithelium differed from the findings in normal bulls. INTRODUCTION The Dag defect was first described in 1966 as an abnormality located in the tail of the sperm of two Jersey bulls which were full brothers (1). Some 40-50 % of the sperm tailsin ejaculated semen were strongly coiled or folded, and split fibrils of the axoneme were often observable in the light microscope (Fig. 1). The two bulls were practically sterile, and it was suggested that the defect might be of hereditary origin. Studies on the ultrastructure of the defect in these bulls (2, 3) and confirmed a few years later in a third Jersey bull (4, 5) showed in transverse sections of the coiled tails that one or several of the doublets and mostly including the adjacent outer dense fibers were lacking in the axonemal unit (Fig. 2 & 3). The complex of coils of individual tails was always found to be enclosed in a common plasma membrane (Fig. 2). (a) This investigation was supported by The State Agricultural and Veterinary Research Council.
DECEMBER 1980 VOL. 14 NO. 6
471
THERIOGENOLOGY In the following years a few more cases were encountered in Danish
bulls, and considering the probability of a hereditary background for this sterilizing sperm defect an experiment was designed with the object of disclosing whether or not it is due to a genetic factor. Attempts to elucidate the pathogenesis of the condition were also included.
Jersey
MATERIALS AND METHODS Spermiograms from a total of 21 Jersey bulls (15 incidentally found, six from breeding experiment) were evaluated using three different preparations (India ink and eosin-nigrosin smears and wet unstained preparation) of each freshly ejaculated semen sample. The total number of abnormal sperm were registered and sperm tail abnormalities were classified in three distinct types, i.e. 1. simple bent, 2. kinked, and 3. coiled/folded tails. The program for testing the heredity of the defect was based on the hypothesis that it is caused by a simple, autosomal, recessive gene, as is the case in a number of inherited defects in cattle. If a bull heterozygous with respect to the Dag defect is mated to his own daughters, one out of eight sons will be homozygous, i.e. possesses the defect. Semen of a bull which was the father of two sons and maternal grandfather of a third with the defect was used for insemination of a sufficient number of his own daughters to produce about 50 sons. All bull calves born as well as their dams were checked for correct paternity by blood group testing. At the age of about 1 month the bull calves were transferred to a breeding station where they were reared under the same conditions as to feeding, management etc. until sexual maturity at which time they underwent a clinical andrological examination. Blood samples were collected for chromosome studies. A minimum of two ejaculates from each bull were examined and bulls with abnormal sperm morphology were transported to the Institute for Animal Reproduction for a closer examination. After completion of the semen investigations the bulls were either castrated or slaughtered, and intensive morphological, histological and biochemical examinations were performed on the testes and epididymides. RESULTS Sperm tail abnormalities in spontaneous cases of the Dag ~- defect Registered spontaneous cases of the defect in Danish Jersey bulls amount to a total of 15 which have been examined during the years 1963 -1979. Systematic morphological semen examinations have been performed on ejaculates collected during periods varying from a few months up to five years. The mean number of Dag defect sperm ranged among bulls from 32 to 71 %.,In comparison the mean number ? s.d. of Dag defect sperm in semen from 131 Jersey bulls (I-12 years old) in normal service at the A.I.stations was 1.40 -I 1.99 % (7). It has been a characteristic feature that the percentage of Dag defect sperm in individual afflicted bulls remains at a constant level throughout the period of investigation. The same is true in ejaculates collected successively in depletion tests which have been performed in a majority of the bulls. Simple bent and kinked tails were present at a lower level, 0.6-15.0 and 7.522.0 %, respectively, and their number tended to vary more between ejaculates in individual bulls. Other sperm abnormalities were within nor-
472
DECEMBER
1980 VOL. 14 NO. 6
THERIOGENOLOGY ma1 limits. Ejaculate volume and sperm concentration were also normal, the motility, however, was low to very low. Sire-daughter test breeding experiment Insemination of 120 daughters with their father's semen resulted in 50 live born bull calves. However, eight of them died within three weeks after parturition, one was slaughtered before maturity, and three had to be rejected because of incorrect paternity of their mothers. The remaining 38 bulls were available for a complete investigation. The first ejaculate was collected when the bulls were between nine and 13 months old. The spermiograms were within normal limits in 29 bulls, while two bulls had an elevated number of simple bent tails (14.3 and 19.2 %). In the remaining seven bulls the level of kinked and coiled/ folded sperm tails was above normal, one bull having 11.6 and 16.5 %, respectively, of these tail abnormalities, while in the other six bulls these sperm defects averaged 20.5 and 43.2 %, respectively, thus conforming to the typical Dag defect. The clinical andrological findings and karyograms were normal in all bulls. Studies on the pathogenesis of the Dag defect As demonstrated previously in one bull (4, 5) the defect arises in the distal part of the epididymal caput. This finding has been confirmed in an additional 17 bulls. Testicular as well as epididymal sperm from the proximal and middle caput have in all cases shown apparently normal morphological structures, and it would be tempting, therefore to assume that a dysfunction of the epididymal epithelium or an abnormal composition of the epididymal plasma might be factors responsible for the development of the defect. Efforts to demonstrate this by histological examination of the epididymal duct and by biophysical and biochemical analysis of the epididymal contents have failed so far to reveal significant differences from the findings obtained in normal bulls. Attempts to induce the defect by adding epididymal sperm from normal bulls to epididymal plasma from defect bulls have also been futile. An increased content of Zn in sperm and plasma of ejaculated semen from Dag defect bulls has been reported recently and it was suggested that a high Zn content could be the inducing factor (4). Studies on epididyma1 sperm regarding Zn and other constituents necessary for the induction of motility are now in progress. DISCUSSION The fact that six bulls from the breeding experiment possessed the typical Dag defect confirms that it is based on an autosomal, recessive factor. The discrepancy between the 15.8 % sons found with the defect and the 12.5 % theoretically expected may be explained in several ways. One reason may be that the material statistically is limited. It cannot be excluded either that there may have been carriers in the population of cows mated with the carrier bull to produce daughters used in the sire-daughter test breeding experiment. Examination of the pedigree for the 15 registered spontaneous cases of the Dag defect gave as a result that the bulls were related in varying degrees and could be traced back in both paternal and maternal lines to a common ancestor, a bull born in 1934. Until recently the Dag defect has only been described in Danish Jersey bulls. In a recent report, however, three apparent cases of the DECEMBER
1980 VOL. 14 NO. 6
473
THERIOGENOLOGY defect have been described in Hereford bulls which were unrelated (8). Other reasons than hereditary ones may thus be operative in the development of the defect. It must be borne in mind, however, that a genetic factor is always to be considered when this congenital defect is present and that many generations may pass from the time carrier parents have been used until the defect appears. REFERENCES 1.
Blom, E. A new sterilizing and hereditary defect (the "Dag-defect") located in the bull sperm tail. Nature (Lond.) 209: 739 (1966).
2.
Blom, E. and Birch-Andersen, A. Ultrastrukturen af en arvelig betinget spermiehaledefekt ("Dag-defekten") hos tyren. Proc. Xth Nord. Vet. Congr. Stockholm 1966, vol. II, p. 699.
3.
Blom, E. and Birch-Andersen, A. The ultrastructure of a new sterilizing defect (the "Dag-defect") in the bull sperm tail. Proc. Vth Congr. Fert. Steril. 1966. Exerpta med. Fdn., Int. Congr. Ser. No. 133, p. 602.
4.
Blom, E. and Wolstrup, C. Zink as a possible causal factor in the sterilizing sperm tail defect, the "Dag-defect", in Jersey bulls. VIIIth Int. Congr. Anim. Reprod. Krakow 1976, vol. I, p. 33.
5.
Koefoed-Johnsen, H.H. and Pedersen, H. Lys- og elektronmikroskopisk undersogelse af et tilfaeldeaf den sdkaldte Dag-defekt i tyrespermiets hale. Kgl. Vet.- og Landbohojsk., Inst. Sterilitetsforskn. Arsberetn. -13: 49 (1970). Kbenhavn.
6.
Koefoed-Johnsen, H.H. and Pedersen, H. Further observations on the Dag-defect of the tail of the bull spermatozoon. J. Reprod. Fertil. -26: 77 (1971).
7.
Pedersen, Hugo, and Koefoed-Johnsen, H.H. Undersogelser over forekomsten af spermiehaleforandringer hos AI tyre af Jerseyrace. Kgl. Vet.- og Landbohojsk., Inst. Sterilitetsforskn. Arsberetn. -22: 37 (1979). Kobenhavn.
8.
Wenkoff, M.S. A sperm mid-piece defect of epididymal origin in two Hereford bulls. Theriogenology ~10: 275 (1978).
474
DECEMBER
1980VOL.14N0.6
THERIOGENOLOGY
Figure
1.
Dag defect or folding
Figure
2.
Electron-micrograph of a transverse section of a strongly coiled tail with an apparently normal mid-piece and lack of a varying number of doublets and outer dense fibers of the principal piece. Dislocated doublets and outer dense fibers are seen outside the fibrous sheath. The complex of coils is surrounded by a common plasma membrane.
Figure
3.
Electron-micrograph of a transverse section of the distal part of the principal piece of a tail with lack of doublets ..._.L 1 n _ .> ”
DECEMBER
sperm (z-nigrosin of the tails around
1980 VOL. 14 NO. 6
smear', with the mid-piece.
strong
cciiing
475
Anderset+),
E. Andresencd
E. Blomce) and H. Philipsenlb) (b) Institute for Animal Reproduction, The Royal Veterinary and Agricultural University (c) The Veterinary Services (d) Department of Genetics of Domestic Animals, The Royal Veterinary and Agricultural University (e) The State Veterinary Serum Laboratory, Copenhagen, Denmark Received for Publication: (j/11/80 ABSTRACT During the period 1963-1979, 15 spontaneous cases of the sterilizing Dag defect of the sperm tail in Danish Jersey bulls have been examined. The pedigree of these bulls could be traced back throuqh both paternal and maternal lines to a common ancestor bull born in 1934. The probable heredity of the defect was tested in a sire-daughter breeding experiment. Six bulls out of 38 sons born produced semen typical of the Dag defect thus confirming that the defect is due to the presence of an autosomal recessive factor. Systematic examination of the epididymal contents from 17 bulls revealed that the defect consistently developed in the distal part of the epididymal caput. Neither biophysical and biochemical qualities of the epididymal contents nor the histological appearance of the duct epithelium differed from the findings in normal bulls. INTRODUCTION The Dag defect was first described in 1966 as an abnormality located in the tail of the sperm of two Jersey bulls which were full brothers (1). Some 40-50 % of the sperm tailsin ejaculated semen were strongly coiled or folded, and split fibrils of the axoneme were often observable in the light microscope (Fig. 1). The two bulls were practically sterile, and it was suggested that the defect might be of hereditary origin. Studies on the ultrastructure of the defect in these bulls (2, 3) and confirmed a few years later in a third Jersey bull (4, 5) showed in transverse sections of the coiled tails that one or several of the doublets and mostly including the adjacent outer dense fibers were lacking in the axonemal unit (Fig. 2 & 3). The complex of coils of individual tails was always found to be enclosed in a common plasma membrane (Fig. 2). (a) This investigation was supported by The State Agricultural and Veterinary Research Council.
DECEMBER 1980 VOL. 14 NO. 6
471
THERIOGENOLOGY In the following years a few more cases were encountered in Danish
bulls, and considering the probability of a hereditary background for this sterilizing sperm defect an experiment was designed with the object of disclosing whether or not it is due to a genetic factor. Attempts to elucidate the pathogenesis of the condition were also included.
Jersey
MATERIALS AND METHODS Spermiograms from a total of 21 Jersey bulls (15 incidentally found, six from breeding experiment) were evaluated using three different preparations (India ink and eosin-nigrosin smears and wet unstained preparation) of each freshly ejaculated semen sample. The total number of abnormal sperm were registered and sperm tail abnormalities were classified in three distinct types, i.e. 1. simple bent, 2. kinked, and 3. coiled/folded tails. The program for testing the heredity of the defect was based on the hypothesis that it is caused by a simple, autosomal, recessive gene, as is the case in a number of inherited defects in cattle. If a bull heterozygous with respect to the Dag defect is mated to his own daughters, one out of eight sons will be homozygous, i.e. possesses the defect. Semen of a bull which was the father of two sons and maternal grandfather of a third with the defect was used for insemination of a sufficient number of his own daughters to produce about 50 sons. All bull calves born as well as their dams were checked for correct paternity by blood group testing. At the age of about 1 month the bull calves were transferred to a breeding station where they were reared under the same conditions as to feeding, management etc. until sexual maturity at which time they underwent a clinical andrological examination. Blood samples were collected for chromosome studies. A minimum of two ejaculates from each bull were examined and bulls with abnormal sperm morphology were transported to the Institute for Animal Reproduction for a closer examination. After completion of the semen investigations the bulls were either castrated or slaughtered, and intensive morphological, histological and biochemical examinations were performed on the testes and epididymides. RESULTS Sperm tail abnormalities in spontaneous cases of the Dag ~- defect Registered spontaneous cases of the defect in Danish Jersey bulls amount to a total of 15 which have been examined during the years 1963 -1979. Systematic morphological semen examinations have been performed on ejaculates collected during periods varying from a few months up to five years. The mean number of Dag defect sperm ranged among bulls from 32 to 71 %.,In comparison the mean number ? s.d. of Dag defect sperm in semen from 131 Jersey bulls (I-12 years old) in normal service at the A.I.stations was 1.40 -I 1.99 % (7). It has been a characteristic feature that the percentage of Dag defect sperm in individual afflicted bulls remains at a constant level throughout the period of investigation. The same is true in ejaculates collected successively in depletion tests which have been performed in a majority of the bulls. Simple bent and kinked tails were present at a lower level, 0.6-15.0 and 7.522.0 %, respectively, and their number tended to vary more between ejaculates in individual bulls. Other sperm abnormalities were within nor-
472
DECEMBER
1980 VOL. 14 NO. 6
THERIOGENOLOGY ma1 limits. Ejaculate volume and sperm concentration were also normal, the motility, however, was low to very low. Sire-daughter test breeding experiment Insemination of 120 daughters with their father's semen resulted in 50 live born bull calves. However, eight of them died within three weeks after parturition, one was slaughtered before maturity, and three had to be rejected because of incorrect paternity of their mothers. The remaining 38 bulls were available for a complete investigation. The first ejaculate was collected when the bulls were between nine and 13 months old. The spermiograms were within normal limits in 29 bulls, while two bulls had an elevated number of simple bent tails (14.3 and 19.2 %). In the remaining seven bulls the level of kinked and coiled/ folded sperm tails was above normal, one bull having 11.6 and 16.5 %, respectively, of these tail abnormalities, while in the other six bulls these sperm defects averaged 20.5 and 43.2 %, respectively, thus conforming to the typical Dag defect. The clinical andrological findings and karyograms were normal in all bulls. Studies on the pathogenesis of the Dag defect As demonstrated previously in one bull (4, 5) the defect arises in the distal part of the epididymal caput. This finding has been confirmed in an additional 17 bulls. Testicular as well as epididymal sperm from the proximal and middle caput have in all cases shown apparently normal morphological structures, and it would be tempting, therefore to assume that a dysfunction of the epididymal epithelium or an abnormal composition of the epididymal plasma might be factors responsible for the development of the defect. Efforts to demonstrate this by histological examination of the epididymal duct and by biophysical and biochemical analysis of the epididymal contents have failed so far to reveal significant differences from the findings obtained in normal bulls. Attempts to induce the defect by adding epididymal sperm from normal bulls to epididymal plasma from defect bulls have also been futile. An increased content of Zn in sperm and plasma of ejaculated semen from Dag defect bulls has been reported recently and it was suggested that a high Zn content could be the inducing factor (4). Studies on epididyma1 sperm regarding Zn and other constituents necessary for the induction of motility are now in progress. DISCUSSION The fact that six bulls from the breeding experiment possessed the typical Dag defect confirms that it is based on an autosomal, recessive factor. The discrepancy between the 15.8 % sons found with the defect and the 12.5 % theoretically expected may be explained in several ways. One reason may be that the material statistically is limited. It cannot be excluded either that there may have been carriers in the population of cows mated with the carrier bull to produce daughters used in the sire-daughter test breeding experiment. Examination of the pedigree for the 15 registered spontaneous cases of the Dag defect gave as a result that the bulls were related in varying degrees and could be traced back in both paternal and maternal lines to a common ancestor, a bull born in 1934. Until recently the Dag defect has only been described in Danish Jersey bulls. In a recent report, however, three apparent cases of the DECEMBER
1980 VOL. 14 NO. 6
473
THERIOGENOLOGY defect have been described in Hereford bulls which were unrelated (8). Other reasons than hereditary ones may thus be operative in the development of the defect. It must be borne in mind, however, that a genetic factor is always to be considered when this congenital defect is present and that many generations may pass from the time carrier parents have been used until the defect appears. REFERENCES 1.
Blom, E. A new sterilizing and hereditary defect (the "Dag-defect") located in the bull sperm tail. Nature (Lond.) 209: 739 (1966).
2.
Blom, E. and Birch-Andersen, A. Ultrastrukturen af en arvelig betinget spermiehaledefekt ("Dag-defekten") hos tyren. Proc. Xth Nord. Vet. Congr. Stockholm 1966, vol. II, p. 699.
3.
Blom, E. and Birch-Andersen, A. The ultrastructure of a new sterilizing defect (the "Dag-defect") in the bull sperm tail. Proc. Vth Congr. Fert. Steril. 1966. Exerpta med. Fdn., Int. Congr. Ser. No. 133, p. 602.
4.
Blom, E. and Wolstrup, C. Zink as a possible causal factor in the sterilizing sperm tail defect, the "Dag-defect", in Jersey bulls. VIIIth Int. Congr. Anim. Reprod. Krakow 1976, vol. I, p. 33.
5.
Koefoed-Johnsen, H.H. and Pedersen, H. Lys- og elektronmikroskopisk undersogelse af et tilfaeldeaf den sdkaldte Dag-defekt i tyrespermiets hale. Kgl. Vet.- og Landbohojsk., Inst. Sterilitetsforskn. Arsberetn. -13: 49 (1970). Kbenhavn.
6.
Koefoed-Johnsen, H.H. and Pedersen, H. Further observations on the Dag-defect of the tail of the bull spermatozoon. J. Reprod. Fertil. -26: 77 (1971).
7.
Pedersen, Hugo, and Koefoed-Johnsen, H.H. Undersogelser over forekomsten af spermiehaleforandringer hos AI tyre af Jerseyrace. Kgl. Vet.- og Landbohojsk., Inst. Sterilitetsforskn. Arsberetn. -22: 37 (1979). Kobenhavn.
8.
Wenkoff, M.S. A sperm mid-piece defect of epididymal origin in two Hereford bulls. Theriogenology ~10: 275 (1978).
474
DECEMBER
1980VOL.14N0.6
THERIOGENOLOGY
Figure
1.
Dag defect or folding
Figure
2.
Electron-micrograph of a transverse section of a strongly coiled tail with an apparently normal mid-piece and lack of a varying number of doublets and outer dense fibers of the principal piece. Dislocated doublets and outer dense fibers are seen outside the fibrous sheath. The complex of coils is surrounded by a common plasma membrane.
Figure
3.
Electron-micrograph of a transverse section of the distal part of the principal piece of a tail with lack of doublets ..._.L 1 n _ .> ”
DECEMBER
sperm (z-nigrosin of the tails around
1980 VOL. 14 NO. 6
smear', with the mid-piece.
strong
cciiing
475