**5. Conclusions**

*Embryology - Theory and Practice*

actin reorganization [12–19].

functions [12, 13].

stage [12, 13, 20].

the oocyte and 452 in the blastocyst [12, 13, 20].

**4.2 Transcription and growth factor genes**

**4.1 Housekeeping gene**

Human genome activation begins in the 4- and 8-cell stages or even in the early 2-cell stage. Data suggest that TE or ICM cell lineage-associated genes are expressed in human embryos later than in mice at around early blastocyst stage, but it is still unclear. Human embryos can be cultured in vitro for 7–8 days post-fertilization. Genes unique in the blastocysts included annexins A2 and A3 (ANXA2, ANXA3), gap junction protein alpha 1 (GJPA1), guanosine triphosphate-binding protein 4 (GTPBP4), and adenosine triphosphatase H.–transporting, lysosomal accessory protein 1 (ATP6AP1). The blastocyst-specific genes were associated with oxidative phosphorylation, glycolysis, and sterol metabolism and were rich in RNA-binding proteins, methyltransferases, gap junction proteins, and intermediate filaments. Oxidative phosphorylation and glycolysis processes control ATP generation during pre-compaction and cavitation stages, respectively. Highly expressed blastocyst genes were involved in the Rho GTPase, control pathway that regulates cytoskeletal changes occurring during cell growth and development; the PDGF pathway, which plays a critical role in cellular proliferation and metabolism, and the integrin signaling pathway are also important in

Studies on gene expression during the preimplantation period have identified transcription factors from housekeeping genes, transcription and growth factor genes, sex-determining genes, tissues specifics, novel genes, and genes of unknown

Housekeeping gene is a gene that plays a role in regulating basal cell function which is important in cell maintenance and also has a specific role in tissues or organisms. Therefore, housekeeping gene is estimated to be expressed in all cells of organism normally, including tissue, external signal, cell cycle, or cell development

Beta-actin, keratin-18, ubiquitous cytoskeletal elements, cell adhesion molecules, and alpha tubulin have been detected, as well as such housekeeping genes as hypoxanthine phosphoribosyl transferase (HPRT), adenosine phosphoribosyl transferase (APRT), glucose-6-phosphate dehydrogenase, hexokinase I, and adenosine deaminase. Overall, out of the 536 housekeeping genes investigated, 427 were detected in

Transcription regulators, growth factors, proto-oncogenes cycle gene cells, and receptors are several genes that expressed during the preimplantation period, including CD44, a cell surface glycoprotein that can play a role in implantation; OCT 4 and OCT 6, transcriptional regulators; cyclin B1, a cell cycle gene; colony stimulating factor 1 receptor, c-fms; tumor necrosis factor and its receptors; interleukin-1 type I receptor (IL-1R tI); growth factors such as insulin and their receptors; epidermal growth factor receptor (EGF-R), epidermal growth factor (EGF),

and transformation of growth factor-alpha (TGF-α) [12, 13, 17–19].

**4.3 Tissue-specific genes, novel genes, and genes of unknown function**

A major histocompatibility complex molecule was detected in preimplantation human embryos and implicated tissue-specific genes as globin and interleukin-10 and also human transposable element, LINE-1, and known expressed sequence tags

**72**

Human preimplantation embryos will become an integral and essential part of such endeavors by setting the genetic foundation that determines the course of human development. It is characterized by reprogramming and programming that encompasses fusion of the egg and sperm pronuclei, epigenetic reprogramming, an extensive wave of degradation of maternal transcripts, and activation of the nascent human embryonic genome. The main objective of blastocyst culture was to increase the success rate of in vitro fertilization (IVF) because of better embryo selection after endometrial synchronicity and/or better genomic activation. Metabolism of the blastocyst occurs in two different places: in trophectoderm cells where glucose consumption occurs and half is converted to lactate, whereas glycolysis occurs in ICM. Morphology of the blastocyst depends on the degree of expansion and ICM and TE morphology. This morphological differentiation was thought to represent the developmental capability of the blastocyst. Gene expression during the preimplantation period has identified transcription factors from housekeeping genes, transcription and growth factor genes, sex-determining genes, tissues specifics, novel genes, and genes of unknown functions. Genes unique in human blastocysts included annexins A2 and A3 (ANXA2, ANXA3), gap junction protein alpha 1 (GJPA1), guanosine triphosphate-binding protein 4 (GTPBP4), and adenosine triphosphatase H.– transporting, lysosomal accessory protein 1 (ATP6AP1). The blastocyst-specific genes were associated with oxidative phosphorylation, glycolysis, and sterol metabolism.

#### **Acknowledgements**

The authors thank all of team Halim fertility center for their help and support to this book.

#### **Conflict of interest**

There is no conflict of interests in this manuscript.
