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Genetics of Endocrine Disorders and Diabetes Mellitus
Published in George H. Gass, Harold M. Kaplan, Handbook of Endocrinology, 2020
Bess Adkins Marshall, Abby Solomon Hollander
Kallmann syndrome is characterized by anosmia and hypogonadotropic hypogonadism. Familial Kallmann syndrome can be transmitted in an X-linked, autosomal recessive, or autosomal dominant fashion.1–6 The X-linked form of the syndrome is the most common, and the gene responsible for this form of the syndrome has been identified. The gene appears to be necessary for proper migration of the cells of the olfactory placode.
The Luteinizing Hormone–Releasing Hormone System in the Developing Monkey Brain
Published in Akira Matsumoto, Sexual Differentiation of the Brain, 2017
Ei Terasawa, Laurie A. Abler, Nancy M. Sherwood
The origin of cLHRH-II cells is currently unknown. However, studies of olfactory ablation suggest that these cells do not originate from the olfactory placode.23,53 It has been suggested that cLHRH-II neurons originate from the ventricular ependymal cells.54,55 In primates as well, cLHRH-II neurons appear to originate from precursor cells in the periventricular zone of the third ventricle and aqueduct, because immunopositive cLHRH-II cells in the area most proximal to the ventricle are more round than those away from the ventricle, and the shape becomes more irregular as the cells move distally from the ventricle (E. Terasawa, unpublished observation).
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
(from Greek, plakos: flat) A thickened sheet of cells found in epithelia (see EPITHELIAL CELLS) during DEVELOPMENT that can serve as a PRIMORDIUM for a structure: the olfactory placode for example is a placode from which elements of the OLFACTORY SYSTEM will develop. See also: neurodevelopment
What are the pharmacological considerations for male congenital hypogonadotropic hypogonadism?
Published in Expert Opinion on Pharmacotherapy, 2022
Giulia Rastrelli, Mario Maggi, Giovanni Corona
Hypogonadotropic hypogonadism (HH) is the failure of the testis to produce testosterone and spermatozoa due to a deficient stimulation by the gonadotropins. This may arise from hypothalamic and/or pituitary defects of different nature. Acquired defects of the hypothalamus-pituitary system are the most common clinical findings, whereas congenital HH (CHH) is rare. CHH may be isolated, when only GnRH release or action is affected, or combined, when other releasing hormones and/or tropins are deficient. The former forms were originally deemed monogenic disorders, but it is now known that multiple genes are often involved. At least 30 genes have been implicated in isolated CHH [1] with an inconsistent genotype–phenotype correlation. These are genes codifying for proteins involved in normal differentiation, development, migration, or action of GnRH neurons from the early embryonal location in the olfactory placode to the hypothalamus or in normal GnRH secretion or action. Normal GnRH neurons development takes place in close relation to that of olfactory nerves; for this reason, isolated CHH may be associated with hypo-anosmia. Although a clear-cut distinction between anosmic and normosmic CHH is not feasible, some genes are most frequently involved in either form. Mutations of ANOS1, FGFR1, PROKR2, PROK2, SEMA3A, and CHD7 are among the most frequently involved in the former, whereas mutations of GNRH1, GNRHR, KISS1, KISS1R, TAC3, and TACR3 are considered specific for the latter [1].
A novel heterozygous intron mutation in SEMA7A causing kallmann syndrome in a female
Published in Gynecological Endocrinology, 2020
Yongting Zhao, Fan Yang, Lili Qiu, Lihong Wang, Hui Che
As we all know, GnRH neurons have intimate connections with olfactory system. In the early stage of embryonic development, GnRH neurons originate from the olfactory placode and migrate along with olfactory axons to the hypothalamus, in which pulsatile GnRH is synthesized and secreted. Then it acts on anterior pituitary, inducing the synthesis and secretion of LH and FSH. The gonadotropins subsequently stimulate gametogenesis and steroidogenesis [4,5]. Recently, with the widespread use of whole exome gene sequencing, about 17 different putative loci of more than 31 loci associated with congenital hypogonadotropic hypogonadism (CHH) are identified to have relations with KS [6]. However, less than 30% of cases have identified relevant pathogenic genes and additional mutations remain to be discovered [7]. Semaphorin 7 A (SEMA7A) is a membrane-anchored guidance molecule of Semaphorin family. Previous studies have demonstrated that SEMA7A mainly acts upon β1-integrin to regulate the migration of GnRH-1 neurons and enhance axon outgrowth in mice [8,9]. Loss of SEMA7A induces tremendous reduction of GnRH-1 neurons in the brain and subfertility. Therefore, SEMA7A is recognized as a genetic marker for GnRH-1 deficiency in human [10]. SEMA7A is also reported to have an association with the phenotype of KS in human [11]. Patients usually present with primary amenorrhea, hypo/anosmia and hypogonadotropic hypogonadism. Some may suffer defects of the skeleton, eye, ear, kidney, and heart. Females usually remain sexually immature, and males exhibit a micropenis or cryptorchidism.
Contemporary genetics-based diagnostics of male infertility
Published in Expert Review of Molecular Diagnostics, 2019
Alberto Ferlin, Savina Dipresa, Andrea Delbarba, Filippo Maffezzoni, Teresa Porcelli, Carlo Cappelli, Carlo Foresta
Kallmann syndrome has a frequency of 1:10.000 and is characterized by hypogonadotropic hypogonadism (HH) (low serum level of testosterone, LH and FSH) and anosmia or hyposmia [68,69]. Beyond HH and midline defects such as cleft palate, other clinical features associated with Kallmann syndrome include tall stature, cryptorchidism, unilateral renal agenesis, and neurogenic deafness [68,69]. The most frequent genetic alteration responsible for this syndrome is a mutation in the X-linked gene KAL1 (14% of familial cases and 11% of sporadic cases), encoding the protein anosmin-1, which is a cell adhesion protein of the extracellular matrix. During embryogenesis, anosmin-1 is required for the organized migration of both olfactory axons and GnRH neurons from the olfactory placode through the cribriform plate and into the preoptic area of the hypothalamus. As such, defects result in anosmia and GnRH deficiency. GnRH deficiency results in subsequent lack of pulsatile LH that is required for normal gonadal function. Recent advance in this field, however, identified many other genes involved in HH mapping on chromosomes other than X chromosome (see below).