Int J Pharm Pharm Sci, Vol 9, Issue 4, 140-143Original Article


KARYOTYPIC ANALYSIS OF CHROMOSOMAL POLYMORPHISM IN RELATION TO REPRODUCTIVE FAILURE

KETAN K. VAGHASIA1, NIDHI D. SHAH1, PARTH S. SHAH1, VIDHI M. BHATT1, SANDIP C. SHAH1*,
MANDAVA V. RAO1,2

1Supratech Micropath Laboratory and Research Institute, 2Ex. Director, School of Sciences, Gujarat University, Ahmedabad, Gujarat India
Email: supratech18@gmail.com

Received: 20 Oct 2016 Revised and Accepted: 27 Feb 2017

ABSTRACT

Objective: This study was undertaken to elucidate the role of heteromorphism in causation of reproductive anomalies like infertility.

Methods: In our study, cytogenetic analysis of 830 suspected referral cases of both sexes were assessed using standard karyotypic technique with Giemsa staining from their blood samples. We identified heteromorphism of D/G groups and non-acrocentric chromosomes following WHO nomenclature.

Results: Our data revealed that most of our heteromorphic cases (38;4.58%) were related to p arm satellites (ps+) of the chromosomes and are related to infertility and abortion. No significant gender variation was noticed in this study.

Conclusion: We hence, suggest that heteromorphism is associated with a loss of reproductive function, as heterochromatin may contain genes that regulate cellular roles in reproduction. Further, it becomes important that such cases are considered for molecular studies, genetic counseling and prenatal/pre-implantation screening.

Keywords: Chromosomal Polymorphism, Reproductive Failure, Cytogenetic Analysis. Acrocentric and non-acrocentric groups, Heterochromatin

© 2017 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4. 0/)
DOI: http://dx.doi.org/10.22159/ijpps.2017v9i4.15787

INTRODUCTION

Repeated DNA sequences in the genome are subject to be heteromorphic and their regions are also highly polymorphic [1]. Chromosomal heteromorphisms include various sizes of heterochromatin blocks, satellites, repeat sequence region and inversion [2]. These heteromorphic variants are most commonly present on non-acrocentric chromosome in the pericentric heterochromatin on long arms (q) of 1, 9 and 16, short arms (p) of acrocentric chromosomes and distal heterochromatin of Y chromosome [2]. Increase/decrease in length of heterochromatin regions of 1, 9, 16 chromosomes (1qh+, 9qh+and 16qh+as well as qh-) and short arms of D and G groups, eg., 13pstk+, 13ps+, 14ps+, 15ps+, 21ps+, Yp+etc. are responsible for reproductive anomalies [3, 4]. Survey showed variants in higher frequency individuals [5]. Reproductive failure is defined as abnormal outcome such as infertility, recurrent spontaneous abortions (RSAs), still birth and bad obstetric history (BOH). Numerous studies revealed the relationship between chromosome heteromorphism and reproductive failure. But controversies also exist [1, 6]. Moreover, studies are rare in population of Gujarat. The role of these heteromorphisms in relation to reproductive failure hence needs to be investigated [4, 7]. Infertility and hyperactivity disorder are also associated with the chromosomal rearrangement [8, 9]. Hence, this study was undertaken to identify heterochromatic regions of acrocentric and paracentric chromosomes in Indian population and their relation to reproductive anomalies at our Research Institute in Ahmedabad, India.

MATERIALS AND METHODS

Patients

We studied 830 referral cases ranging in age between 20-40 y collected from different regions of India, over two years (2014-2016) at Supratech Micropath Research Institute, Ahmedabad referred with suspected or established reproductive issues. They were asked to collect blood samples as per our instructions after filling patients’ consent form. This work is approved by Gujarat University (GU) human ethical committee (GU/HEC/001/15) for investigation.

Karyotypic analysis and heteromorphism

The peripheral blood samples of all patients were cultured for 72 h following the method of Moorhead et al. [10]. For each case, 20 metaphase plates containing chromosome plates deemed appropriate quality were analyzed on an automated Meta Systems of Carl Ziess for karyotypic study and heteromorphism was reported according to ISCN of WHO [11]. Satellite stalks (stk) and satellites (s) of D and G groups and non-acrocentric chromosomes including Y chromosome length variations were included in this report. Statistical analysis was done as appropriate and frequencies and percentage of each variant was calculated.

RESULTS

Out of the total number of 830 referral cases analyzed, Only 38 cases (4.58%) were detected to have heteromorphisms in their karyotypes.

A: D and G group satellites on short arm (P) (ps+)

13ps+Variant: The frequency was more in males (3) than females (2) and the percent was found to be 14.2 in both male and females having infertility and recurrent miscarriages (RMCs) (table 1, fig. 3).

14ps+Variant: This frequency was more in females (4) comparatively. Only one male case was affected. The total percent was 13.2 exhibiting above mentioned anomalies (table 1, fig. 3).

15ps+Variant: The frequency was found to be more in females (3) comparatively. The percent was like that of 13 chromosome (14.2%) and exhibited infertility (table 1, fig. 3).

21ps+Variant: The frequency was higher in males (4) than the opposite sex (2) and the percent was also more than all above variants (15.9%) with infertility and recurrent spontaneous abortions (RSAs) (table 1, fig. 3).

22ps+Variant: It had the highest incidence amongst all heteromorphisms detected in our study. Males (6) are affected comparatively with higher frequency with (21.2%) which was significant causing sterility and RSAs (table 1, fig. 3).

13ps+, 14ps+, 15ps+, 21ps+, 22ps+variants: All variants were present in karyotype of one female. Percentage and frequency were same. This case had (BOH) with infertility and recurrent spontaneous abortions (RSAs) (table 1, fig. 1, 3)

Table 1: Gender wise heteromorphic frequencies of D and G Groups

Karyotypes Gender Frequency M-16 Frequency F-14 Total frequency Percentage (%) Anomalies
46,XY,13ps+ 3 0.089 - 0.142 14.2 Infertility and
46,XX,13ps+ 2 - 0.053 RMCs
46,XY,14ps+ 1 0.027 - 0.133 13.3 Infertility and
46,XX,14ps+ 4 - 0.106 RMCs
46,XY,15ps+ 2 0.053 - 0.142 14.2 Infertility and
46,XX,15ps+ 3 - 0.089 RMCs
46,XY,21ps+ 4 0.106 - 0.159 15.9 Infertility and
46,XX,21ps+ 2 - 0.053 RSAs
46,XY,22ps+ 6 0.159 - 0.080 08.0 Infertility and
46,XX,22ps+ 2 - 0.053 RSAs

46XX,13ps+,14ps+,

15ps+,21ps+,22ps+

 1 - 0.027 0.027 02.7 BOH and Abortion

Bad obstetric history= BOH., RSAs= Recurrent spontaneous abortions., RMCs= Recurrent miscarriages., M=Male., F=Female.


Fig. 1: Female karyotype showing multiple heteromorphisms of D and G groups, (46, XX, 13ps+, 14ps+, 15ps+, 21ps+and 22ps+)

Fig. 2: Sample patient karyotype showing heterochromatin variants of 9 and Y chromosomes and inversion (Y)

B: Heteromorphic variation in 9 and Y Chromosomes

We did not detect any heteromorphisms in 1 and 16 chromosomes.

9qh+Variants: It was found on chromosome 9 and frequency detected was 0.089 in females (3) and 0.053 in males (2).

Its calculated percent was (14.2%) possessing reproductive malformation included infertility and RSAs (table 2, fig. 4).

Inv (Y) and Yp+: These were present in the male. Frequency of inversion Y is more (2) than that of Yp+(1). Similarly percent was also higher in respect to inversions (5.3%) and elucidated with infertility including abortions (table 2, fig. 2, 4).

Table 2: Gender wise status of heteromorphic frequencies of 9 and ‘Y’ chromosomes with percent

Karyotype Male (2) frequency Female (3) frequency Total frequency Percent (%) Anomalies
46,XY,9qh+ 0.053 - 0.142 14.2 Infertility and
46,XX,9qh+ - 0.089 Abortion

Y-Chromosome length

Variation (Male)
46,XY,inv(Y) 0.053 (2) - 0.05 5.3 Infertility
46,XY,Yp+ 0.027 (1) - 0.02 2.7 Infertility

Figure in parenthesis indicate case numbers of males/females


Fig. 3: Percent (%) distribution of variants in D and G groups


Fig. 4: Percent (%) distribution of chromosomal heteromorphism of 9 and Y

DISCUSSION

In our study 38 karyotypes with heteromorphic variants were detected. These included acrocentric chromosomal satellites, (ps+) and non-acrocentric chromosomes 9 with qh+ and Y–chromosome length variation p+(Yp+) and inv(Y) in our study.

There are various reports which are controversial on clinical effects of chromosome variants with respect to reproductive failure [1, 4, 7, 12]. Earlier heterochromatin is considered to be ‘Junk’ inert DNA. But now it is known to be essential for cell viability and fertility as it contains genes for their vital activities [4]. It also plays an important role in spindle attachment and chromosome movement, meiotic paring and sister chromatid exchange (SCE) cohesion [12, 13]. Sofia et al. [14] noticed the secondary construction variation regions and satellite alterations among individuals with reproductive failure. Mierla and Stolan [15], Christofolini et al. [2] and Pokale [16] stressed the role of satellite variants of acrocentric and non-acrocentric chromosomes in induction of recurrent spontaneous abortions (RSAs), recurrent miscarriages (RMCs), still birth and male infertility strongly supporting our data.

In our data high frequency of D and G group variants (ps+) were noticed in both sexes. The percent of 22ps+was higher (21.2%) followed by 21ps+(15.9%) and others (14.2%; 13ps+, 14ps+and 15ps+;13.3%) respectively. Madon et al. [4] documented these variants in their study were correlated with reproductive effects followed by chromosomal rearrangements of inv(9) and inv(Y) in both cases in support of our data. Moreover, we observed in our study that heteromorphism of ps+in all D and G groups was observed leading to multiple clinical effects in the female patient with bad obstetric history (BOH) too. Sofia et al. [14] and Pokale [16] detected satellite karyotypes of acrocentric chromosome in both cases as mentioned earlier that D/G groups with heterochromatin variants led to infertility, spontaneous recurrent abortions (RSAs) and recurrent miscarriages (RMCs) with BOH [1, 2, 7, 15, 17].

Christofolin et al., [2] and Ogata et al., [18] reported Y length variation and 22ps+variants in the male affecting its development and fertility in support of our data, where inv(Y) and Yp+are related to male reproductive failure (8%) as it is known to be more polymorphic in Asians [19,20]. Recently other workers [7, 16, 21] studied the inversion 9 and Y chromosomes causing multiple effects in female and male partners, supporting our observation where 9qh+contributed 14.2% in causation of clinical effects. Boronova et al., [22] and Purandare et al. [7] provided an exhaustive review in regard to heteromorphic variations in acrocentric and non-acrocentric chromosomes to which our data corroborates.

Though the role of heteromorphic variants in etiology of RSA/RMC and infertility is not well understood earlier, it is now considered [23] that heterochromatien properties and molecular composition are similar to that chromosomal regions involved in gene silencing, position effect variegation and X-chromosome inactivation [23]. The appearance of a specific kind of chromatin packaging initiated by epigenetic signals in DNA like gene promoter hyper methylation and histone acetylation is necessary for activation and silencing of genes. A high incidence of chromosomal variants in infertile men/women is suggestive of large heterochromatin blocks responsible for weakening of chromosome pairing, spindle fiber attachment or down regulation of active genes for meiotic arrest in gametogenesis to cause sterility. Further nuclear organizer region (NOR), stalks of satellites and satellites having heterochomatin are present in acrocentric and paracentric chromosomes (1, 13, 19). Their variations in heterochromatin under influence of heat stimuli such as heat shock and heat shock protein (HSP) assembly and epigenetic signals play a role in gene regulation and control affecting reproductive function in both cases [24-26]. Previously, Boronova et al., [22], Pokale, [16] and Mau et al., [27] have documented that heterochromatin regions contain high amount of DNA and is heterogenous. Chromosomal variants are an expression of morphologic variability chromosome related modifications in amount of heterochromatin. It is hence believed that an increase in heterochromatin might develop the risk of nondisjunction of chromosome segregation leading to chromosomally unbalanced gamete formation in both sexes. Further variation in heterochromatin in centromere causes defects in its function and kinetochore assembly causing abnormal homologous chromosome pairing and impacts on cell division affecting gamete formation[7, 22] leading to reproductive ill effects. However other investigators [21, 28, 29] suggested an incidence of chromosomal variants need to be debatable and further search is necessary to identify genes responsible for normal reproduction in heterochromatic regions of acrocentric and non-acrocentric groups and their activation and inactivation mechanisms.

CONCLUSION

We hence conclude that karyotypic analysis and heteromorphism of the D/G groups and 9 chromosomes with chromosomal re-arrangements found in our study are related to infertility, and other anomalies. It is therefore suggestive that couples undergo cytogenetic detection followed by genetic analysis. The recent molecular methods probably may unveil the relation between heteromorphism and reproductive failure as we know that heterochromatin has been regarded now playing crucial cellular roles.

ACKNOWLEDGEMENT

Authors are thankful to all staff of Supratech Micropath Research Institute, Ahmedabad for their assistance.

CONFLICT OF INTERESTS

No conflicts of interest noticed amongst authors

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