Epididymides of sex‐reversed XX mice lack the initial segment

Lebarr, Deborah K.; Blecher, Stan R.

doi:10.1002/dvg.1020070206

Cited by 22 publications

(5 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There is much interconnectivity between the capillaries surrounding the initial segment duct. The vascular arrangement surrounding the initial segment duct is absent in Ros1 knockout and XX sex reversed ( XXSxr ) mice [ 85 ], presumably due to the failure of the initial segment to develop. Further studies showed that the loss of the initial segment in XXSrx males was androgen-independent [ 85 ], maybe pointing to the role of testicular factors.…”

Section: Lack Of Initial Segment Results In Male Infertilitymentioning

confidence: 99%

“…The vascular arrangement surrounding the initial segment duct is absent in Ros1 knockout and XX sex reversed ( XXSxr ) mice [ 85 ], presumably due to the failure of the initial segment to develop. Further studies showed that the loss of the initial segment in XXSrx males was androgen-independent [ 85 ], maybe pointing to the role of testicular factors. These studies also demonstrated the intimate relationship between development of the initial segment and concomitant development of its vasculature.…”

Section: Lack Of Initial Segment Results In Male Infertilitymentioning

confidence: 99%

See 1 more Smart Citation

Is the Epididymis a Series of Organs Placed Side By Side?

Domeniconi

Souza

et al. 2016

Biology of Reproduction

View full text Add to dashboard Cite

The mammalian epididymis is more than a highly convoluted tube divided into four regions: initial segment, caput, corpus and cauda. It is a highly segmented structure with each segment expressing its own and overlapping genes, proteins, and signal transduction pathways. Therefore, the epididymis may be viewed as a series of organs placed side by side. In this review we discuss the contributions of septa that divide the epididymis into segments and present hypotheses as to the mechanism by which septa form. The mechanisms of Wolffian duct segmentation are likened to the mechanisms of segmentation of the renal nephron and somites. The renal nephron may provide valuable clues as to how the Wolffian duct is patterned during development, whereas somitogenesis may provide clues as to the timing of the development of each segment. Emphasis is also placed upon how segments are differentially regulated, in support of the idea that the epididymis can be considered a series of multiple organs placed side by side. One region in particular, the initial segment, which consists of 2 or 4 segments in mice and rats, respectively, is unique with respect to its regulation and vascularity compared to other segments; loss of development of these segments leads to male infertility. Different ways of thinking about how the epididymis functions may provide new directions and ideas as to how sperm maturation takes place.

show abstract

Section: Lack Of Initial Segment Results In Male Infertilitymentioning

confidence: 99%

Section: Lack Of Initial Segment Results In Male Infertilitymentioning

confidence: 99%

Is the Epididymis a Series of Organs Placed Side By Side?

Domeniconi

Souza

et al. 2016

Biology of Reproduction

View full text Add to dashboard Cite

show abstract

“…These three models differ from the Pax8 knockout in having full spermatogenesis and an epididymis containing spermatozoa. Another model lacking the initial segment is the chromosomal anomaly sex-reversed pseudohermaphrodism (XXsr; LeBarr & Blecher 1986), and these, like the Pax8 knockout, lack spermatozoa in the epididymis, but as a result of a complete absence of germ cells, reflecting the chromosomal condition.…”

Section: Trbmentioning

confidence: 99%

Male congenital hypothyroid Pax8−/− mice are infertile despite adequate treatment with thyroid hormone

Wistuba¹,

Mittag²,

Luetjens³

et al. 2007

Journal of Endocrinology

View full text Add to dashboard Cite

Severe forms of congenital hypothyroidism lead to serious clinical symptoms if thyroid hormone replacement therapy is not instituted immediately after birth. In this study, Pax8mice that are born without a thyroid gland were used as an animal model to study the consequences of congenital hypothyroidism. As expected, adequate treatment of these animals with thyroxine restored the general deficits of congenital hypothyroidism; however, Pax8-deficient male mice were infertile. We report here that in these mice, the efferent ducts and epididymides are either absent or the efferent ducts exhibit a reduced lumen and extensive connective tissue, which appears to impair testicular drainage and subsequently leads to complete absence of spermatozoa from the epididymis. The results suggest that, starting with the onset of pubertal testicular fluid secretion, a backpressure is created in the testis by the absence of efferent ducts or constriction of their tubule lumen when present. This subsequently leads to secondary disorganization of the seminiferous epithelium that increases with age, resulting in mixed atrophy of the testis in the adult. Serum testosterone levels as well as mRNA expression of anterior pituitary hormones are in the normal range, indicating that the observed infertility is not due to hormonal imbalance, but rather to a developmental defect of the efferent ducts. The demonstration of Pax8 expression in the epithelia of the epididymis and the efferent ducts suggests a direct morphogenic role of Pax8 in the development of these organs. It remains to be elucidated whether congenital hypothyroid male patients with mutations in the Pax8 gene are similarly affected.

show abstract

“…Though the adult pseudomale has testosterone levels as high as or higher than the normal XY male, the epididymis lacks the important initial segment [LeBarr and Blecher, 1986] (Fig. 4) and the abnormality is present before the pubertal androgen surge [LeBarr et al, 1991], again suggesting a non‐hormonally mediated effect of sex‐determining genes.…”

Section: Effects Of Sex Determining Factors On Organs Other Than Gonadsmentioning

confidence: 99%

Genetics of sexual development: A new paradigm

Blecher

Erickson

2007

American J of Med Genetics Pt A

Self Cite

View full text Add to dashboard Cite

The classical paradigm of human and mammalian sexual development, largely based on work of Alfred Jost, depicts the genetic factor(s) that determine(s) sex as influencing only the fate of the gonad. A maleness factor produces testes (Primary Sex Determination). These organs secrete hormones which cause male Secondary Sexual Differentiation. In absence of the maleness factor, by default the gonad becomes an ovary, and the absence of testicular hormones leads to female secondary differentiation. In this article a new paradigm is proposed, to accommodate recent findings. Sexual dimorphism precedes gonadal development, in a Pregonadal Stage. Furthermore, female development is not by default-both male (Y) and female (X) sex-chromosomal primary sex-determining mechanisms probably exist. The human/mammalian male Y-chromosomal sex-determining gene is now known (SRY/Sry), and a candidate for a non-inactivated, X-linked, female determining factor, is under study. However, the proximate gonad-determining genes are probably on autosomes. Pathways between the primary factors and the proximate gonad-determining genes are indirect and complex. A hypothetical gene Z has been proposed, that inhibits the testis determiner and is itself the target of suppression by SRY/Sry. Candidates for proximate testis and ovary-determining factors and for Z also exist. The "default" concept has also been superseded with respect to secondary sexual differentiation. Absence of testicular hormones does not produce a normal female phenotype; ovarian genes and hormones are necessary. Finally, sex-chromosomal sex-determining genes influence the development not only of non-gonadal organs of secondary sexual development, but also of organs outside of the reproductive system.

show abstract

Epididymides of sex‐reversed XX mice lack the initial segment

Cited by 22 publications

References 21 publications

Is the Epididymis a Series of Organs Placed Side By Side?

Is the Epididymis a Series of Organs Placed Side By Side?

Male congenital hypothyroid Pax8−/− mice are infertile despite adequate treatment with thyroid hormone

Genetics of sexual development: A new paradigm

Contact Info

Product

Resources

About